A multi-element alloy silver-free copper-based solder and preparation method thereof

Abstract

The present invention provides a multi-element alloy silver-free copper-based solder and a preparation method thereof, wherein the solder comprises the following components in percentage by mass: 30-40% zinc, 4%-11% manganese, 1%-4% tin, 0.2%-0.6% silicon, 0.2%-1% rare earth elements, and the balance is copper, wherein the rare earth elements include cerium, praseodymium and rhenium, and the mass ratio of cerium, praseodymium and rhenium is (0.8-1.2): (0.8-1.2): (0.6-1.0). The multi-element alloy silver-free copper-based solder of the present invention improves the performance of the brazed joint, including improving the strength, toughness and fatigue resistance of the joint, and ensures the reliability and stability of the connection under various working conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of brazing, and in particular relates to a multi-element alloy silver-free copper-based brazing filler metal and a preparation method thereof. Background Art

[0002] In modern manufacturing, brazing technology is widely used to connect various metal parts to achieve structural integrity and functionality. With the continuous improvement of brazing material performance requirements and the need for cost control, silver-free copper-based brazing filler metals have gradually attracted attention.

[0003] Before the emergence of silver-free copper-based solder, common solders included silver-containing solders. Silver-containing solders have good wetting properties and connection strength, but the price of silver is high, which leads to an increase in solder costs. In addition, traditional copper-based solders may have deficiencies in certain properties, such as poor oxidation resistance, unsatisfactory high-temperature strength, and limited wetting ability for certain special materials.

[0004] Currently, the high cost of silver-containing solders limits their widespread use in some cost-sensitive applications. Traditional copper-based solders have poor oxidation resistance and are easily oxidized in high-temperature environments, affecting the quality and reliability of brazed joints. Some traditional copper-based solders have insufficient high-temperature strength, which may lead to joint failure under high-temperature working conditions. The wetting ability of some special materials, such as stainless steel and high-temperature alloys, is insufficient, making it difficult to achieve high-quality brazing connections. Summary of the invention

[0005] In view of this, the present invention aims to overcome the defects in the prior art and proposes a multi-alloy silver-free copper-based solder and a preparation method thereof, which has good wettability to stainless steel and can be used to braze stainless steel, while reducing the brazing melting point to achieve high efficiency and energy saving.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] In a first aspect, the present invention provides a multi-alloy silver-free copper-based solder, comprising the following components in percentage by mass:

[0008] Zinc 30-40%, manganese 4%-11%, tin 1%-4%, silicon 0.2%-0.6%, rare earth elements 0.2%-1%, and the balance is copper, wherein the rare earth elements include cerium, praseodymium and rhenium, and the mass ratio of cerium, praseodymium and rhenium is (0.8-1.2):(0.8-1.2):(0.6-1.0).

[0009] Rare earth elements have the function of preventing oxidation and improving wettability during brazing heating. The addition of rare earth element Ce in the brazing filler metal can reduce the harmful effects of impurity elements at the grain boundaries, strengthen the grain boundaries, refine the structure, and the addition of Ce can inhibit the formation of some brittle compounds; the Pr element can improve the wetting and spreading properties of the brazing filler metal to a certain extent, and can improve the microstructure of the brazing filler metal alloy; the Re element can reduce the surface tension of the alloy, improve the thermal fatigue performance, and can greatly improve the wettability of the alloy.

[0010] After adding Pr and Ce elements, a low melting point eutectic phase containing rare earth will be formed. The existence of this eutectic phase further reduces the liquidus temperature of the solder, thereby expanding the process window of the solder and allowing the brazing operation to be carried out within a more suitable temperature range. The subsequent mixing with Re can greatly enhance the wettability of the solder.

[0011] In addition, Ce has excellent oxygen storage and release capabilities, Pr can assist Ce in redox reactions, and Re can further enhance this anti-oxidation synergistic effect. During the brazing process and subsequent use of the joint, they will form a stable oxide protective film on the surface of the brazing material. This oxide film can not only prevent oxygen from penetrating into the brazing material, but also prevent the metal elements (copper, zinc) in the brazing material from reacting with the corrosive media in the surrounding environment.

[0012] The rare earth elements mixed with Pr, Ce and Re can inhibit the growth of grains and form a fine and uniform grain structure in the solder. Fine grains can improve the yield strength and toughness of the solder. At the same time, these three rare earth elements can also strengthen the bond between the solder and the base material. They can react with the alloying element manganese in the base material to generate strengthening phases such as intermetallic compounds. These strengthening phases are distributed at the interface between the solder and the base material and inside the solder, thereby improving the mechanical properties of the brazed joint such as tensile strength and shear strength, so that the brazed joint can better withstand various forms of loads such as tension, shearing and bending. At the same time, the inventor innovatively discovered that when the total content of rare earth elements is less than 0.2%, it will not work. When the content exceeds 1%, it will not only be difficult to smelt, but also cause casting defects, so the content is preferably 0.2%-1%.

[0013] In some embodiments, the mass ratio of cerium, praseodymium, and rhenium is 1:1:1.

[0014] In some embodiments, the mass percentage of copper is 53%-58%. The copper content in the solder of the present invention should not be too high. Within this ratio range, the alloy can be guaranteed to have a lower melting point. However, when the copper content is lower than 53%, the cold rolling performance of the alloy deteriorates, which is not conducive to alloy processing.

[0015] After zinc is added to copper, the melting temperature of the brazing material is significantly reduced. When the zinc content reaches 30%, the melting point of copper drops to 950°C, and its structure is a single α solid solution. At this time, the alloy has high strength and good plasticity. When the zinc content exceeds 40%, the melting temperature of copper can drop to about 905°C, but the β phase appears at room temperature, and the plasticity of copper decreases. As the zinc content increases, the mechanical properties of the alloy gradually deteriorate.

[0016] In some embodiments, the mass percentage of manganese is 10%. After adding manganese to the solder, the melting temperature of copper is significantly reduced. When the manganese content is 10%, the melting point can be reduced to about 870°C. At this time, the alloy has higher strength and plasticity. When the manganese content exceeds 11%, the cold rolling performance of the alloy decreases.

[0017] Silicon can significantly reduce the melting temperature of copper, increase the hardness of the alloy, and improve the corrosion resistance of copper. When the silicon content is 0.2%-0.6%, the alloy has the best plasticity; in addition, when zinc and silicon are added to copper at the same time, silicon can reduce the volatilization of zinc during brazing.

[0018] Tin can significantly reduce the melting temperature of copper. Adding a small amount of tin to copper-zinc alloy can improve the fluidity of the alloy. At the same time, tin will reduce the solubility of zinc in copper. As the tin content increases, the plasticity of the alloy will decrease significantly.

[0019] In some embodiments, the melting point of the multi-alloy silver-free copper-based solder is solidus ≤ 780°C, liquidus ≤ 793°C, and the spreading area is ≥ 172 mm 2 , tensile strength ≥534MPa, elongation ≥20%, shear strength of stainless steel brazing ≥208MPa.

[0020] In some embodiments, the melting point of the multi-alloy silver-free copper-based solder is 770-780°C for the solidus, 778-793°C for the liquidus, and the spreading area is 172-775mm 2 , tensile strength 534 ~ 555MPa, elongation 20% ~ 22%, shear strength of stainless steel brazing 208 ~ 217MPa.

[0021] In some embodiments, the multi-alloy silver-free copper-based solder is heated and melted in an atmospheric environment at 250°C, and the mass of the oxide slag after 30 minutes is ≤1.10 g; in a neutral 3.5% NaCl solution, the corrosion potential is ≤-0.0995 V, and the corrosion current density is ≤4.12×10 -6 A.

[0022] In some embodiments, the multi-alloy silver-free copper-based solder is heated and melted in an atmospheric environment at 250°C, and the mass of the oxidized slag after 30 minutes is 0.79 to 1.10 g; in a neutral 3.5% NaCl solution, the corrosion potential is -0.0873 to -0.0995 V, and the corrosion current density is 3.85×10 -6 ~4.12×10 -6 A.

[0023] In a second aspect, the present invention provides a method for preparing the above-mentioned multi-alloy silver-free copper-based solder, comprising the following steps: adding copper and manganese into a smelting device, adding tin after melting, and finally adding rare earth elements, silicon and zinc, and then casting an ingot, heating and extruding it into a wire or rolling it into a foil.

[0024] In the preparation method, Cu and Mn are added first to lower the melting point, Sn is added after melting to further lower the melting point, and finally rare earth elements, silicon and zinc are added.

[0025] In some embodiments, the rare earth elements cerium, praseodymium and rhenium are respectively wrapped with copper sheets before being added, and then put into the smelting equipment after being wrapped. Since rare earths are relatively active and easy to burn, the rare earths are wrapped with copper sheets before smelting, which can not only reduce the melting time of the rare earths, but also reduce the amount of rare earth burnout.

[0026] In a third aspect, the present invention also provides the application of the above multi-element alloy silver-free copper-based solder, especially in salt bath brazing, furnace brazing, flame gas welding and high-frequency brazing.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) The multi-element alloy silver-free copper-based solder of the present invention avoids the use of expensive silver elements, thereby reducing the material cost of the solder while ensuring the brazing performance, thereby meeting a wider market demand and reducing production costs.

[0029] (2) The multi-alloy silver-free copper-based solder of the present invention improves the performance of the brazed joint, including improving the strength, toughness, fatigue resistance, etc. of the joint, thereby ensuring the reliability and stability of the connection under various working conditions.

[0030] (3) The multi-element alloy silver-free copper-based solder of the present invention has enhanced oxidation resistance and corrosion resistance, reduces the effects of oxidation and corrosion on the brazed joints during the brazing process and in the use environment, and prolongs their service life.

[0031] (4) The multi-element alloy silver-free copper-based solder of the present invention meets environmental protection requirements, reduces or avoids the use of elements and substances that are harmful to the environment, and complies with increasingly stringent environmental regulations and standards. DETAILED DESCRIPTION

[0032] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0033] The present invention will be described in detail below with reference to the embodiments.

[0034] Example 1

[0035] A multi-element alloy silver-free copper-based solder comprises the following components in percentage by mass:

[0036] 30% zinc, 10% manganese, 2% tin, 0.3% silicon, 0.2% rare earth elements, and the balance is copper, wherein the rare earth elements include cerium, praseodymium and rhenium, and the mass ratio of cerium, praseodymium and rhenium is 1:1:1.

[0037] The preparation method of the above multi-element alloy silver-free copper-based solder comprises the following steps:

[0038] (1) The rare earth elements cerium, praseodymium and rhenium are each wrapped with a copper sheet with a thickness of 1 mm and a mass of 30 g;

[0039] (2) Add copper and manganese into the smelting equipment and heat until they are completely melted;

[0040] (3) After copper and manganese are melted, add tin and continue heating until it is completely melted;

[0041] (4) putting the wrapped rare earth elements cerium, praseodymium and rhenium into a smelting device;

[0042] (5) Finally, add silicon and zinc and continue heating until all metals are completely melted and mixed evenly;

[0043] (6) Pour the smelted alloy liquid into a casting mold and obtain an alloy ingot after cooling and solidification;

[0044] (7) The alloy ingot is heated and then extruded into a wire shape by an extruder.

[0045] Example 2

[0046] A multi-element alloy silver-free copper-based solder comprises the following components in percentage by mass:

[0047] 33% zinc, 7% manganese, 3% tin, 0.5% silicon, 0.2% rare earth elements, and the balance copper, wherein the rare earth elements include cerium, praseodymium and rhenium, and the mass ratio of cerium, praseodymium and rhenium is 0.8:1.2:0.7. The preparation method of the above multi-element alloy silver-free copper-based solder is the same as that of Example 1.

[0048] Example 3

[0049] A multi-element alloy silver-free copper-based solder comprises the following components in percentage by mass:

[0050] 40% zinc, 4% manganese, 2% tin, 0.6% silicon, 0.4% rare earth elements, and the balance copper, wherein the rare earth elements include cerium, praseodymium and rhenium, and the mass ratio of cerium, praseodymium and rhenium is 1.2:1.1:0.6. The preparation method of the above multi-element alloy silver-free copper-based solder is the same as that of Example 1.

[0051] Example 4

[0052] A multi-element alloy silver-free copper-based solder comprises the following components in percentage by mass:

[0053] 36% zinc, 4% manganese, 1% tin, 0.2% silicon, 0.8% rare earth elements, and the balance copper, wherein the rare earth elements include cerium, praseodymium and rhenium, and the mass ratio of cerium, praseodymium and rhenium is 1.1:0.8:1.0. The preparation method of the above multi-element alloy silver-free copper-based solder is the same as that of Example 1.

[0054] Example 5

[0055] A multi-element alloy silver-free copper-based solder comprises the following components in percentage by mass:

[0056] 30.5% zinc, 11% manganese, 4% tin, 0.5% silicon, 1% rare earth elements, and the balance is copper, wherein the rare earth elements include cerium, praseodymium and rhenium, and the mass ratio of cerium, praseodymium and rhenium is 1:1:1. The preparation method of the above multi-element alloy silver-free copper-based solder is the same as that of Example 1.

[0057] Comparative Example 1

[0058] The multi-component alloy silver-free copper-based solder of this comparative example includes the following components in percentage by mass: 30% zinc, 10% manganese, 2% tin, 0.3% silicon, and the balance is copper. The preparation method of the multi-component alloy silver-free copper-based solder is the same as that of Example 1.

[0059] Comparative Example 2

[0060] The multi-component alloy silver-free copper-based solder of this comparative example includes the following components in mass percentage: 30% zinc, 10% manganese, 2% tin, 0.3% silicon, 0.2% rare earth element, and the balance is copper, wherein the rare earth element includes cerium and praseodymium, and the mass ratio of cerium to praseodymium is 1:1. The preparation method of the multi-component alloy silver-free copper-based solder is the same as that of Example 1.

[0061] Comparative Example 3

[0062] The multi-component alloy silver-free copper-based solder of this comparative example includes the following components in mass percentage: 30% zinc, 10% manganese, 2% tin, 0.3% silicon, 0.2% rare earth element, and the balance is copper, wherein the rare earth element includes praseodymium and rhenium, and the mass ratio of praseodymium to rhenium is 1:1. The preparation method of the multi-component alloy silver-free copper-based solder is the same as that of Example 1.

[0063] Comparative Example 4

[0064] The multi-component alloy silver-free copper-based solder of this comparative example includes the following components in percentage by mass: 30% zinc, 10% manganese, 2% tin, 0.3% silicon, 0.2% rare earth element, and the balance is copper, wherein the rare earth element includes cerium and rhenium, and the mass ratio of praseodymium to rhenium is 1:1. The preparation method of the multi-component alloy silver-free copper-based solder is the same as that of Example 1.

[0065] Comparative Example 5

[0066] The multi-component alloy silver-free copper-based solder of this comparative example includes the following components in mass percentage: 30% zinc, 10% manganese, 2% tin, 0.3% silicon, 0.2% rare earth element, and the balance is copper, wherein the rare earth element includes cerium, praseodymium and rhenium, and the mass ratio of cerium, praseodymium and rhenium is 1:1:2. The preparation method of the multi-component alloy silver-free copper-based solder is the same as that of Example 1.

[0067] Comparative Example 6

[0068] The multi-component alloy silver-free copper-based solder of this comparative example includes the following components in percentage by mass: 30% zinc, 10% manganese, 2% tin, 0.3% silicon, 1.1% rare earth elements, and the balance is copper, wherein the rare earth elements include cerium, praseodymium, and rhenium, and the mass ratio of cerium, praseodymium, and rhenium is 1:1:1. The preparation method of the multi-component alloy silver-free copper-based solder is the same as that of Example 1.

[0069] Comparative Example 7

[0070] The multi-alloy silver-free copper-based solder of this comparative example includes the following components in percentage by mass: 30% zinc, 10% manganese, 2% tin, 0.3% silicon, 0.6% rare earth elements, and the balance copper, wherein the rare earth elements include cerium, praseodymium and rhenium, and the mass ratio of cerium, praseodymium and rhenium is 1:1:1.

[0071] Comparative Example 8

[0072] The multi-element alloy silver-free copper-based solder of this comparative example is different from Example 1 in that the rare earth elements cerium, praseodymium and rhenium are directly put into the smelting equipment without being wrapped with copper.

[0073] The solders prepared in Examples 1 to 5 and Comparative Examples 1 to 6 were subjected to performance tests, and the test process was as follows: the melting point of the solder was measured using a differential thermal analyzer; the spreading area of ​​the solder was measured in a box-type resistance furnace, the size of the experimental steel plate was 40*40*3mm, the test solder was 200mg, and the test temperature was 115-125°C higher than the melting point of the solder; the tensile strength, shear strength and elongation were tested using the method in GB / T228.1-2021; (200±0.5) g of the sample was heated and melted in an atmospheric environment at 250°C, and the surface of the molten solder was scraped every 10 min, with a heating cycle of 10, 20, 30 min, The antioxidant capacity of different solders was compared by comparing the mass change of oxide slag over time. The mass of oxide slag of the solder within a certain period of time was inversely proportional to the antioxidant capacity. The solder was placed on stainless steel and heated to melt and spread. Then, a 1cm×1cm area was selected in the spreading area for wire cutting. Finally, the obtained sample was polished and cleaned to obtain an electrochemical sample. The polarization curve of the solder electrochemical sample was tested in a neutral 3.5% NaCl solution at room temperature using a three-electrode system to obtain the corrosion potential (Ecorr) and corrosion current density (Icorr) of the sample.

[0074] The test results are shown in the table below:

[0075]

[0076] From the above test results, it can be seen that the synergistic combination of the three rare earths Pr, Ce, and Re can significantly improve the strength and toughness of the solder and the mechanical properties of the brazed joint, such as tensile strength and shear strength, and the content of 0.2%-1% can not only ensure the above effects but also ensure easy smelting; because rare earths are more active and easy to burn, the rare earths are wrapped with copper sheets before smelting, which can not only reduce the melting time of the rare earths, but also reduce the amount of rare earth burn. In addition, it can be seen from the above table that the solder of Example 1, which has a formula of 30% zinc, 10% manganese, 2% tin, 0.3% silicon, 0.2% rare earth elements, and the balance is copper, and the mass ratio of the rare earth elements cerium, praseodymium, and rhenium is 1:1:1, has the best comprehensive performance.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-element alloy silver-free copper-based solder, characterized in that: The composition includes the following mass percentages: Zinc 30-40%, manganese 4%-11%, tin 1%-4%, silicon 0.2%-0.6%, rare earth elements 0.2%-1%, and the balance is copper, wherein the rare earth elements include cerium, praseodymium and rhenium, and the mass ratio of cerium, praseodymium and rhenium is (0.8-1.2):(0.8-1.2):(0.6-1.0).

2. The multi-element alloy silver-free copper-based solder according to claim 1, characterized in that: The mass ratio of cerium, praseodymium and rhenium is 1:1:

1.

3. The multi-component alloy silver-free copper-based solder according to claim 1, characterized in that: The mass percentage of the copper is 53%-58%.

4. The multi-component alloy silver-free copper-based solder according to claim 1, characterized in that: The mass percentage of manganese is 10%.

5. The multi-component alloy silver-free copper-based solder according to claim 1, characterized in that: The melting point of the multi-element alloy silver-free copper-based solder is solidus ≤ 780°C, liquidus ≤ 793°C, and the spreading area is ≥ 172 mm 2 , tensile strength ≥534MPa, elongation ≥20%, shear strength of stainless steel brazing ≥208MPa.

6. The multi-component alloy silver-free copper-based solder according to claim 1, characterized in that: The multi-element alloy silver-free copper-based solder is heated and melted in an atmospheric environment at 250°C, and the mass of the oxide slag after 30 minutes is ≤1.10g; in a neutral 3.5% NaCl solution, the corrosion potential is ≤-0.0995 V, and the corrosion current density is ≤4.12×10 -6 A.

7. The method for preparing the multi-component alloy silver-free copper-based solder according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: adding copper and manganese into a smelting device, adding tin after melting, and finally adding rare earth elements, silicon and zinc, and then ingot casting, heating and extruding into wire or rolling into foil.

8. The method for preparing the multi-component alloy silver-free copper-based solder according to claim 7, characterized in that: The rare earth elements cerium, praseodymium and rhenium are respectively wrapped with copper sheets before being added, and then put into the smelting equipment after being wrapped.

9. Use of the multi-alloy silver-free copper-based solder according to any one of claims 1 to 6 in salt bath brazing, furnace brazing, flame gas welding and high frequency brazing.

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