High-strength cadmium-free low-silver silver brazing filler

Abstract

The application discloses a high-strength cadmium-free low-silver silver brazing filler metal. The silver brazing filler metal is composed of 7.5-8.5% of Ag, 38.5-43.5% of Zn, 14.5-15.5% of Sn, 5.0-5.5% of Ni, 0.0005-0.001% of nano NbBe 12 , 0.0005-0.001% of nano MoBe 12 , and the balance of Cu, wherein the solidus temperature of the silver brazing filler metal is less than or equal to 660 DEG C, and the liquidus temperature is less than or equal to 720 DEG C. When the silver brazing filler metal is used in brazing purple copper-Q235 steel, purple copper-yellow copper, yellow copper-stainless steel with a commercially available FB102 brazing flux, the shear strength of the brazed joint is significantly higher than that of the existing BAg12CuZn(Si) brazing filler metal and BAg5CuZn(Si) brazing filler metal.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of brazing materials of metal materials, and relates to a high-strength cadmium-free low-silver silver brazing material. BACKGROUND

[0002] With the increase of the use amount of silver brazing material, in order to reduce the material cost, the demand for low-silver silver brazing material is increasing, especially the low-silver silver brazing material with a silver content lower than 20% and high strength and low solid-liquid phase line temperature (such as a melting temperature range of 680 DEG C to 745 DEG C to meet the brazing of copper and copper alloy structures) has been a product in urgent need in the market. The existing documents such as BAg20CuZn (Si) brazing material recommended in GB / T 10046-2018 "Silver Brazing Material" has a melting temperature range of solidus 690 DEG C, but the liquidus 810 DEG C is too high to meet the requirements; the BAg5CuZn (Si) brazing material with a low silver content in GB / T 10046-2018 "Silver Brazing Material" has a melting temperature range of solidus 820 DEG C and liquidus 870 DEG C; and the BAg12CuZn (Si) brazing material has a melting temperature range of solidus 800 DEG C and liquidus 830 DEG C. The above two low-silver brazing materials provide users with the choice of reducing cost, but the solidus and liquidus temperatures of the brazing material are higher than 800 DEG C, which is easy to cause "overburning" and "softening" of copper and copper alloy (such as the melting point of H58 brass is about 934 DEG C to 967 DEG C), which is not conducive to the brazing of copper and copper alloy structures. Therefore, the development of cadmium-free low-silver silver brazing material with lower silver content and better performance has been a hot topic for technical personnel in the related manufacturing industry.

[0003] The inventors found through literature retrieval that there are only a few examples of new low-silver brazing filler metals in published Chinese patent documents. For example, document CN 116871736A reports a cadmium-free low-silver brazing filler metal and its preparation method. The cadmium-free low-silver brazing filler metal is composed of 4.0-5.0% Ag, 40.0-45.0% Zn, 11.0-13.0% Sn, 0.5-1.5% In, 0.5-1.5% Ga, 0.5-1.5% Ni, 0.01-0.05% nano-CeO2, 0.01-0.05% nano-Y2O3, and the balance Cu. The solidus temperature of the brazing filler metal of the invention is ≤735℃, and the liquidus temperature is ≤780℃. Document CN 115533365A reports a cadmium-free low-silver brazing filler metal, characterized by a mass percentage composition of 8.0-10.0% Ag, 38.0-42.0% Zn, 6.0-10.0% Sn, 1.5-2.5% In, 1.5-2.5% Ga, 1.5-2.5% Ni, 0.0001-0.0005% nano-HfC, 0.0001-0.0005% nano-ZrC, and the balance Cu. The solidus temperature of the brazing filler metal of the invention is ≤700℃, and the liquidus temperature is ≤750℃. The Ag content of the above two low-silver brazing filler metals is less than or equal to 10%, but both contain a high content of In and Ga elements, resulting in a high cost. Numerous studies have shown that the common feature of reducing the melting temperature (such as the solidus temperature and the liquidus temperature) of cadmium-free silver brazing filler metal is the addition of at least one or more low-melting-point elements such as Sn (melting point 231.9℃), In (melting point 156.6℃), Ga (melting point 29.76℃), Li (melting point 180.5℃), and alloy elements such as Ni that can reduce the melting point of the brazing filler metal. Since In, Ga, and Li are "rare elements", the annual production worldwide is also very limited. The price of In and Ga is comparable to or higher than that of silver. It can be seen that adding In and Ga elements to reduce the melting temperature of silver brazing filler metal is not the best choice. Due to the rapid development of new energy vehicles, the price of Li has also skyrocketed in recent years to 300 million yuan / ton (3000 yuan / kg), which is much higher than that of Cu (about 80 yuan / kg). Therefore, the addition of Li also greatly reduces the value of mass production and application. The price of Sn is not high compared to Ag, and the reserves are relatively abundant. However, a large amount of Sn addition can lead to the formation of hard and brittle intermetallic compounds Cu6Sn5, making the silver brazing filler metal "difficult to process", so the addition of Sn is generally difficult to exceed 10%.According to the literature GB / T 10046-2018 "silver brazing filler metal", it is known that the addition amount of Sn in the known high-Sn brazing filler metal is 9.5%~10.5% in BAg60CuSn brazing filler metal, and is generally 1.5%~2.5% in Ag-Cu-Zn-Sn series brazing filler metal, and only a few types such as BAg56CuZnSn have Sn addition amount of 4.5%~5.5%.

[0004] Although the literature CN 115533365A reports that the addition amount of Sn can be as high as 10.0%, the solidus temperature of the obtained cadmium-free low-silver brazing filler metal is ≤700℃, and the liquidus temperature is ≤750℃; the literature CN 116871736A reports that the addition amount of Sn can be as high as 11.0%~13.0%, and the solidus temperature thereof is ≤735℃, and the liquidus temperature is ≤780℃, which is close to or even better than the melting temperature of BAg20CuZn(Si) brazing filler metal, and basically meets the brazing requirements of copper and copper alloy structures.

[0005] However, since the above-mentioned cadmium-free low-silver brazing filler metal all adds a high content of In and Ga elements, in addition to the high cost factor, In and Ga belong to "rare metals", and both the earth's reserves and the world's annual output are very small, which is not suitable for large-scale use. Therefore, how to use the abundant Sn element to replace In and Ga, and add In and Ga elements as "trace elements" to achieve the purpose of reducing the melting temperature of the new brazing filler metal and improving the strength of the brazing filler metal, further research and discussion are needed. SUMMARY

[0006] The purpose of the present application is to provide a high-strength cadmium-free low-silver silver brazing filler metal, which has an Ag content of 7.5%~8.5%, a liquidus temperature of ≤750℃, and is suitable for brazing of red copper-H58 brass, red copper-Q235 steel, brass-304 stainless steel and other materials, meeting the needs of brazing filler metal users to reduce costs, improve product quality and enhance market competitiveness.

[0007] The technical solution for achieving the purpose of the present application is as follows:

[0008] A high-strength cadmium-free low-silver silver brazing filler metal, with a mass percentage ratio of: 7.5%~8.5% Ag, 38.5%~43.5% Zn, 14.5%~15.5% Sn, 5.0%~5.5% Ni, 0.0005%~0.001% nano-NbBe 12 , 0.0005%~0.001% nano-MoBe 12 , and the balance being Cu.

[0009] Further, the nano-NbBe 12 or nano-MoBe 12The particle size is 50nm-100nm.

[0010] The high-strength cadmium-free low-silver silver brazing filler described in the application uses silver plate, cathode copper, zinc ingot, tin ingot and metal nickel in a proportioning manner, and is smelted by using a medium-frequency smelting process. Before casting, trace nanometer NbBe 12 and MoBe 12 powder are wrapped with red copper foil, and then are quickly inserted into a molten brazing filler liquid in a graphite bell jar, and after stirring, the brazing filler is cast into an ingot, and then through extrusion and drawing, the required brazing filler wire is obtained.

[0011] The solidus temperature of the brazing filler is less than or equal to 660 DEG C, and the liquidus temperature is less than or equal to 720 DEG C. When the brazing filler is used for brazing red copper-Q235 steel, red copper-yellow copper and yellow copper-stainless steel in cooperation with a commercially available FB102 flux, the shear strength of the brazed joint is significantly higher than that of the existing BAg12CuZn(Si) brazing filler and BAg5CuZn(Si) brazing filler.

[0012] In the application, the content of metal nickel is increased to 5.0%-5.5%, and NbBe 12 (melting point 1690 DEG C) and MoBe 12 (melting point 1705 DEG C) are used as nucleation points of the low-silver silver brazing filler and modifiers of Cu6Sn5, so that the low-silver silver brazing filler can be successfully processed into wire when the content of Sn is as high as 14.5%-15.5%, and the melting temperature of the brazing filler is significantly reduced, i.e. the solidus temperature is less than or equal to 660 DEG C, and the liquidus temperature is less than or equal to 720 DEG C. DETAILED DESCRIPTION

[0013] Compared with the prior art, the technical scheme of the application creatively solves the following key technical problems:

[0014] (1) It is found that in the high-strength cadmium-free low-silver silver brazing filler with a silver content of 7.5%-8.5%, the addition of trace nanometer NbBe 12 and MoBe 12 (particle size 50nm-100nm) can significantly refine Cu6Sn5 grains and significantly inhibit the generation of Cu6Sn5, and at the same time, the content of Ni is significantly increased to 5.0%-5.5%, which can significantly convert the brittle and hard Cu6Sn5 into a (Cu,Ni)6Sn5 intermetallic compound with better plasticity, so that the brazing filler of the application can be successfully processed into wire even when the content of Sn is as high as 14.5%-15.5%.

[0015] Although the document CN 115533366A reports that in high-tin copper-phosphorus brazing filler metal, adding trace amounts of rare earth metal Sm, metal Yb element and trace amounts of nano Sm2O3, nano Yb2O3 oxide can significantly refine the grain size of copper-phosphorus brazing filler metal, especially the grain size of intermetallic compounds Cu6Sn5 and (Cu, Ni)6Sn5, but the maximum particle size of the intermetallic compound (i.e. (Cu, Ni)6Sn5) can only reach ≤5μm, and the addition amount of Sn in the brazing filler metal can only reach 8.0%~11.0%. However, the technical solution of adding trace amounts of nano NbBe 12 , MoBe 12 in the present application can refine the maximum particle size of intermetallic compounds Cu6Sn5 and (Cu, Ni)6Sn5 to ≤2.5μm, so that the brazing filler metal of the present application can be successfully processed into wire even when the Sn content is as high as 14.5%~15.5%, which is not achieved by the prior art and has not been reported. In addition, the addition of Sn content of 14.5%~15.5% also significantly reduces the melting temperature range of the high-strength cadmium-free low-silver silver brazing filler metal of the present application to ≤660℃ solidus and ≤720℃ liquidus, compared with the solidus 820℃ and liquidus 870℃ of BAg5CuZn(Si) brazing filler metal, fully meeting the brazing requirements of copper and copper alloy structures.

[0016] (2) It is found that adding Ni content to 5.0%~5.5% can significantly convert brittle and hard Cu6Sn5 into (Cu, Ni)6Sn5 intermetallic compound with better plasticity; at the same time, adding trace amounts of nano NbBe 12 , MoBe 12 , and using the "synergistic effect" of Ni and nano NbBe 12 , nano MoBe 12 , can refine the maximum particle size of Cu6Sn5 and (Cu, Ni)6Sn5 to ≤2.5μm, so that the brazing filler metal of the present application can be successfully processed into wire even when the Sn content is as high as 14.5%~15.5%. In the present application, the high-strength cadmium-free low-silver silver brazing filler metal is strengthened by "fine-grain strengthening", which not only significantly improves the plasticity of the brazing filler metal, but also makes the new brazing filler metal easy to process without the need to adjust the original equipment and process during extrusion and drawing. In addition, the strength of the brazing joint of the new brazing filler metal is also significantly improved (more than 30% higher than the brazing joint strength of BAg5CuZn(Si) brazing filler metal and BAg12CuZn(Si) brazing filler metal), which is not achieved by the prior art and has not been reported.

[0017] The experiment finds that the high-strength cadmium-free low-silver silver brazing filler metal has the following advantages: compared with BAg12CuZn(Si) and BAg5CuZn(Si) brazing filler metals, the spreading area of the brazing filler metal on red copper, H58 brass, Q235 steel and 304 stainless steel is significantly improved by more than 20%; the tensile strength (σ b ) and the shear strength (τ) of the brazing seam are both increased by more than 30%, which is far higher than the brazing seam strength of BAg12CuZn(Si) and BAg5CuZn(Si) brazing filler metals, as shown in Table 1.

[0018] The nano NbBe 12 and the nano MoBe 12 can be commercially available or synthesized by a chemical reduction method. The technical solutions of the present application are further described in detail in combination with specific examples.

[0019] Example 1

[0020] A high-strength cadmium-free low-silver silver brazing filler metal has the following component proportions by mass percentage: 7.5% of Ag, 43.5% of Zn, 14.5% of Sn, 5.5% of Ni, 0.0005% of nano NbBe 12 , 0.001% of nano MoBe 12 , and the balance of Cu.

[0021] The high-strength cadmium-free low-silver brazing filler metal obtained by using the above component proportions has a solidus of ≤660°C and a liquidus of ≤720°C (both considering measurement errors). The wetting and spreading performance of the brazing filler metal on red copper, H58 brass, Q235 steel and 304 stainless steel is excellent. When the brazing filler metal is used in a flame brazing manner and matched with FB102 flux, the brazing seam strength of the brazing seam obtained when the following combinations of base materials are used is shown in the brackets: red copper-H58 brass (σ b = 270±10 MPa, τ = 265±10 MPa), red copper-Q235 steel (σ b = 360±10 MPa, τ = 360±10 MPa), H58 brass-304 stainless steel (σ b = 370±10 MPa, τ = 365±10 MPa). The brazing seam strength of the brazing filler metal is significantly higher than the brazing seam strength of BAg12CuZn(Si) and BAg5CuZn(Si) brazing filler metals obtained under the same conditions.

[0022] Example 2

[0023] A high-strength cadmium-free low-silver silver brazing filler metal has the following component proportions by mass percentage: 8.5% of Ag, 38.5% of Zn, 15.5% of Sn, 5.0% of Ni, 0.001% of nano NbBe 12 , 0.0005% of nano MoBe 12, balance Cu.

[0024] The high-strength cadmium-free low-silver solder obtained by using the above component ratio has a solidus of ≤660℃ and a liquidus of ≤720℃ (both considering measurement errors). The wetting and spreading performance on red copper, H58 brass, Q235 steel and 304 stainless steel is excellent. When flame brazing is used in combination with FB102 flux, the brazing seam strength of the solder is as shown in the brackets when the following combinations of base materials are brazed: red copper-H58 brass (σ b =270±10MPa, τ=265±10MPa), red copper-Q235 steel (σ b =360±10MPa, τ=360±10MPa), H58 brass-304 stainless steel (σ b =370±10MPa, τ=365±10MPa). The brazing seam strength of the solder is significantly higher than that of BAg12CuZn(Si) solder and BAg5CuZn(Si) solder under the same conditions.

[0025] Example 3

[0026] A high-strength cadmium-free low-silver solder, with a mass percentage ratio of: 8.0% Ag, 41.5% Zn, 15.0% Sn, 5.25% Ni, 0.0008% nano-NbBe 12 , 0.0008% nano-MoBe 12 , balance Cu.

[0027] The high-strength cadmium-free low-silver solder obtained by using the above component ratio has a solidus of ≤660℃ and a liquidus of ≤720℃ (both considering measurement errors). The wetting and spreading performance on red copper, H58 brass, Q235 steel and 304 stainless steel is excellent. When flame brazing is used in combination with FB102 flux, the brazing seam strength of the solder is as shown in the brackets when the following combinations of base materials are brazed: red copper-H58 brass (σ b =270±10MPa, τ=265±10MPa), red copper-Q235 steel (σ b =360±10MPa, τ=360±10MPa), H58 brass-304 stainless steel (σ b =370±10MPa, τ=365±10MPa). The brazing seam strength of the solder is significantly higher than that of BAg12CuZn(Si) solder and BAg5CuZn(Si) solder under the same conditions.

[0028] Comparative Example 1

[0029] A cadmium-free low-silver solder, with a mass percentage ratio of: 8.0% Ag, 41.5% Zn, 15.0% Sn, 0.0008% nano-NbBe12 0.0008% nano-MoBe 12 balance Cu.

[0030] The cadmium-free low-silver solder obtained by using the above component ratio has no change in solidus temperature and liquidus temperature (e.g., solidus temperature ≤ 660°C, liquidus temperature ≤ 720°C (both considering measurement errors)), but the processability is significantly reduced. The wetting and spreading performance on red copper, H58 brass, Q235 steel and 304 stainless steel is also significantly worse than that of the embodiment. When the soldering filler metal is used in the flame soldering mode and matched with FB102 flux, the solder joint strength of the following combinations of soldered base materials is reduced (see the data in parentheses): red copper-H58 brass (σ b = 250 ± 10 MPa, τ = 245 ± 10 MPa), red copper-Q235 steel (σ b = 340 ± 10 MPa, τ = 335 ± 10 MPa), H58 brass-304 stainless steel (σ b = 345 ± 10 MPa, τ = 335 ± 10 MPa).

[0031] The solder joint strength of the solder of Comparative Example 1 is higher than that of BAg12CuZn(Si) solder and BAg5CuZn(Si) solder under the same conditions, but is significantly lower than that of Example 1, Example 2 and Example 3.

[0032] Comparative Example 2

[0033] A cadmium-free low-silver solder, with a component ratio by mass percentage of: 8.0% Ag, 41.5% Zn, 15.0% Sn, 5.25% Ni, and balance Cu.

[0034] The cadmium-free low-silver solder obtained by using the above component ratio has no change in solidus temperature and liquidus temperature (e.g., solidus temperature ≤ 660°C, liquidus temperature ≤ 720°C (both considering measurement errors)), but the processability is significantly reduced. The wetting and spreading performance on red copper, H58 brass, Q235 steel and 304 stainless steel is also significantly worse than that of the embodiment. When the soldering filler metal is used in the flame soldering mode and matched with FB102 flux, the solder joint strength of the following combinations of soldered base materials is reduced (see the data in parentheses): red copper-H58 brass (σ b = 250 ± 10 MPa, τ = 245 ± 10 MPa), red copper-Q235 steel (σ b = 340 ± 10 MPa, τ = 335 ± 10 MPa), H58 brass-304 stainless steel (σ b = 345 ± 10 MPa, τ = 335 ± 10 MPa).

[0035] The brazing joint strength of the solder of Comparative Example 2 is higher than that of BAg12CuZn(Si) solder and BAg5CuZn(Si) solder under the same conditions, but is significantly lower than that of Example 1, Example 2 and Example 3.

[0036] Table 1 shows the spreading performance (spreading area, mm2) and brazing joint strength data of the solders of Examples 1-3, commercially available BAg5CuZn(Si) solder and commercially available BAg12CuZn(Si) solder. 2 As can be seen from the data of Comparative Example 1 and Comparative Example 2, the solder wetting and spreading performance is deteriorated and the mechanical properties of the brazing joint are significantly decreased by adding metal Ni or nano-NbBe, nano-MoBe, nano-CrBe alone. 12 12 12 12

[0037] Table 1

[0038] ​​​​

Claims

1. A high-strength cadmium-free low-silver silver brazing material, characterized by comprising, in mass %, The mass percentage ratio is: 7.5% to 8.5% of Ag, 38.5% to 43.5% of Zn, 14.5% to 15.5% of Sn, 5.0% to 5.5% of Ni, 0.0005% to 0.001% of nano NbBe 12 , 0.0005% to 0.001% of nano MoBe 12 , and the balance is Cu.

2. The high-strength, cadmium-free, low-silver silver brazing alloy of claim 1, wherein, nanometer NbBe 12 or nanometer MoBe 12 with a particle size of 50-100 nm.

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