Solder for graded welding of honeysuckle silk jewelry

Abstract

The invention discloses a welding flux for graded welding of honeysuckle silk jewelry, which comprises a high-temperature-grade welding flux, a medium-temperature-grade welding flux and a low-temperature-grade welding flux, the high-temperature-grade welding flux comprises 0-2% of copper, 0.01-5% of zinc, 0.01-3% of indium, 0.01-0.4% of germanium, 0.01-0.95% of tin, 0.01-0.1% of rare earth and the balance of silver; the medium-temperature-level solder comprises 18%-19.5% of copper, 0.1%-2% of zinc, 0.1%-2% of indium, 0.01%-0.5% of tin, 0.01%-0.5% of germanium, 0.01%-0.1% of rare earth and the balance silver. The low-temperature solder comprises 18%-21% of copper, 12%-14% of zinc, 0.1%-1% of indium, 0.1%-1% of tin, 0.01%-0.5% of germanium, 0.01%-0.1% of rare earth and the balance silver. The solder has excellent welding performance and corrosion resistance, the color of the solder is close to that of pure silver, and the preparation process and mechanical property requirements of different solder forms can be met.

Description

Technical Field

[0001] This invention relates to the field of jewelry solder technology, and in particular to a solder for graded welding of silver filigree jewelry. Background Technology

[0002] The basic process of filigree involves drawing materials such as gold and silver into wires of different specifications. Then, through several of the eight major techniques—pinching, filling, piling, stacking, weaving, stitching, assembling, and welding—the wires are shaped and processed into blanks of various shapes, structures, and patterns. Finally, the blanks undergo surface treatment to enhance their quality and color. Filigree reached a high level of artistry in the mid-to-late Ming Dynasty, particularly excelling in weaving and piling techniques, and often employing kingfisher feather inlay to achieve a magnificent and resplendent effect.

[0003] In making silver filigree jewelry, silver bars are first rolled into thin rods, then drawn into fine wires. Two or more strands of wire are then twisted together to create various patterns. Tweezers or pliers are used to shape the wires into various designs, which are then filled or stacked within a specified pattern to form different shapes. Solder powder is sifted evenly through a small sieve, and the patterns are then welded together. Filigree jewelry is often composed of several filigree components, which need to be assembled into a whole through a process called "assembly." After assembly, they must be fixed by welding. However, for complex designs, some parts are difficult to weld after assembly (colloquially known as "not resistant to heat"), and the blank is easily melted when the heat is increased.

[0004] Filigree work requires welding to form the jewelry, involving numerous and widely distributed welding points that need to be worked on multiple times. Therefore, the solder used is of high quality. There are various types of filigree solder, categorized into high-melting-point, medium-melting-point, and low-melting-point solders. During production, the appropriate solder is selected based on the different parts of the jewelry and the specific manufacturing process, and the solder is then prepared into powder form.

[0005] Filigree work demands high welding skills, especially in the precise control of flux properties, flux dosage, and welding temperature. Problems include poor flux properties leading to poor weldability, easy oxidation and impurity formation, unsuitable flux melting point, low weld strength, poor flux corrosion resistance, and difficulty in electroplating the welded area. Too little flux results in areas without weld or weak welds; too much flux creates unsightly weld scars, increasing subsequent cleaning work. An excessively strong welding flame can melt the delicate filigree into gold beads, ruining the entire work; too little flame makes it difficult to weld.

[0006] Traditional silver wire inlay craftsmanship has developed unique formulas and preparation processes over a long period, and modern silver wire inlay production largely continues these practices. Silver wire inlay solder mainly includes several types: old flux, yellow flux, red flux, and new flux. Old flux, also known as 80% silver flux, contains 80% silver, with the remainder being brass or copper. Old flux using brass has a melting point of 810℃, while old flux using copper has a melting point of 850℃. Old flux has good fire resistance and is often used for welding in the first stage of the process, forming the base. Yellow flux, also known as 60% silver flux, is made from silver and brass, containing approximately 60% silver, with a melting point of 720℃. Red flux is also a 60% silver flux, containing 60% silver, with a melting point of 780℃. Yellow and red flux are mainly used for seam welding. New flux is made from silver, brass, and copper, also a 60% silver flux, containing 60% silver, with a melting point of 740℃, and is used for welding large products. These silver wire inlay solders mainly have the following problems:

[0007] (1) The overall purity of the soldering flux is low, with the purity of the old flux being only 80%, and the purity of the yellow and red flux being even lower, at 66%. In order for the purity of silver wire products to meet the requirements of pure silver, although the purity of the wire used is above 99.9%, a large amount of soldering flux is used in the production of wire, especially the large amount of old flux. Its purity directly affects the purity of the product, which will lead to the problem of the product not meeting the purity standard.

[0008] (2) A certain amount of Cd is often added to the flux formulation to lower the melting point of the alloy; and during the flux melting process, a considerable amount of arsenic trioxide is added for stirring to improve the wettability and flowability of the flux. Since the vapors of Cd metal and oxides are highly toxic, and arsenic trioxide, commonly known as arsenic, is a highly toxic substance, it is harmful to human health during alloy smelting and welding.

[0009] (3) Bletilla striata is needed as an adhesive in the production of filigree to fix the filigree to the mold, and then welding flux is sieved for welding. However, the current red flux has poor tolerance to Bletilla striata and is prone to forming slag, which affects the welding effect.

[0010] (4) The new drug is a welding flux developed in the 1970s for welding large products. It combines the advantages of yellow and red flux, but it is easy to break off when welding in a large fire.

[0011] (5) Filigree work is often combined with enamel work to achieve better decorative effects and artistic value. Enamel firing requires a relatively high temperature, usually between 600 and 800°C. Therefore, appropriate solder needs to be selected according to the firing conditions of the enamel. However, existing solders have many problems in terms of melting point compatibility and resistance to oxidation and discoloration.

[0012] Therefore, traditional silver filigree solders have certain problems in terms of color assurance, welding performance, and environmental safety, and cannot well meet the current needs of filigree jewelry production. Although many silver solders have been developed for industrial applications in recent years, many of them are not specifically developed for the special process of filigree jewelry and are not suitable for welding filigree jewelry. For example, patent 201210281681.4 discloses a silver solder and its preparation method, with a chemical composition of 23-60% Ag, 38-75% Cu, and 0.01-2% P, and a melting point of about 780℃. However, this solder cannot meet the requirements of filigree jewelry in terms of either color or melting point. Patent 201611247738.3 discloses a silver-based solder without a separator and its preparation method. This solder does not contain the harmful element cadmium and its chemical composition is 39-41% Ag, 29.5-31.5% Zn, 1.3-1.7% Ni, 0.1-0.2% In, 2.5-3.5% Sn, 0.05-0.1% Co, 0.01-0.02% graphene, with Cu as the balance. It exhibits good spreadability and plasticity when welding stainless steel, but its color and melting point distribution are not suitable for welding filigree jewelry. Patent 02106267.6 discloses an Ag solder for welding and a brazing method using it. This solder has a chemical composition of 1-10% Sn, 2.5-10% Cu, <6% Mn, 0.1-2.5% Ni, with the balance being Ag. This solder can improve welding strength by adding Ni and Mn, with a melting temperature range of 800-900℃ and a silver content of up to 96%. However, this solder is mainly for vacuum welding of hermetically sealed components and cannot meet the welding requirements of jewelry under atmospheric conditions. Furthermore, it lacks a melting point gradation, failing to meet the requirements for graded welding. Patent 201611147938.1 discloses a solder powder formulation method for silver filigree jewelry. It uses 100g of pure silver, 38g of copper solder rod, and 6g of brass to prepare the solder powder, resulting in a melting point of 680℃. However, the silver content is only 56%, and it also lacks a melting point gradation, failing to meet the requirements for graded welding of filigree jewelry. Moreover, the traditional mechanical grinding process used in preparing the solder powder inevitably results in the inclusion of grinding debris from the grinding tools, causing solder powder defects. Summary of the Invention

[0013] To overcome the shortcomings of existing technologies, this invention provides a graded solder for silver filigree jewelry. Addressing the problem that existing silver solders cannot adequately meet the needs of graded welding in silver filigree jewelry, this invention optimizes the solder formula for high-temperature, medium-temperature, and low-temperature welding. The highest liquidus temperature of the solder does not exceed 910℃, and the lowest solidus temperature is not lower than 670℃, with a welding temperature range of 60-80℃, providing good controllability. The purity of the high-temperature solder is not less than 93%, the medium-temperature solder not less than 80%, and the low-temperature solder not less than 65%, significantly reducing the risk of insufficient purity in filigree products. The graded solder possesses excellent welding and corrosion resistance properties, a color close to pure silver, and can meet the preparation process and mechanical property requirements of different solder morphologies.

[0014] This invention is achieved using the following technical solution:

[0015] A type of solder for graded welding of silver filigree jewelry includes high-temperature solder, medium-temperature solder and low-temperature solder. The high-temperature solder is used for the first or initial welding of the workpiece, the medium-temperature solder is used for intermediate welding after the workpiece is welded with high-temperature solder, and the low-temperature solder is used for the final assembly welding after the workpiece is welded with medium-temperature solder.

[0016] The high-temperature solder comprises the following components by mass percentage:

[0017] Copper 0-2.0% (inclusive), zinc 0.01-5.0%, indium 0.01-3.0%, tin 0.01-0.95%, germanium 0.01-0.4%, rare earth elements 0.01-0.1%, the remainder being silver, and unavoidable impurity elements;

[0018] Medium-temperature solder comprises the following components by weight percentage:

[0019] Copper 18.0–19.5%, zinc 0.1–2.0%, indium 0.1–2.0%, tin 0.01–0.5%, germanium 0.01–0.5%, rare earth elements 0.01–0.1%, the remainder being silver, and unavoidable impurity elements;

[0020] Low-temperature solder comprises the following components by weight percentage:

[0021] Copper 18.0–21.0%, zinc 12.0–14.0%, indium 0.1–1.0%, tin 0.1–1.0%, germanium 0.01–0.5%, rare earth elements 0.01–0.1%, the remainder being silver, and unavoidable impurity elements.

[0022] Among the above materials, silver is pure silver with a content of 99.95 wt% or higher, copper is pure copper with a content of 99.95 wt% or higher, zinc is pure zinc with a content of 99.95 wt% or higher, indium is pure indium with a content of 99.95 wt% or higher, tin is pure tin with a content of 99.95 wt% or higher, and germanium is pure germanium with a content of 99.95 wt% or higher.

[0023] In this invention, the basic approach followed in developing the solder for graded welding of silver filigree jewelry is as follows:

[0024] (1) Filigree jewelry has a complex and delicate structure, which needs to be broken down into several parts and manufactured and assembled by process. The manufacturing process requires multiple welding steps. Subsequent welding is carried out on the basis of the previous welding. The previous welding is the basis for subsequent welding and processing. Therefore, it is necessary to reasonably control the melting point and melting temperature range of the high-temperature solder, so that it is both far from the melting point of the welding substrate itself and has a sufficiently high melting point to withstand the heating during subsequent welding. This will leave enough room for the welding operation, avoid the risk of the welded parts remelting and disintegrating, and ensure the safety of the welded workpiece and the operability of the welding process.

[0025] (2) On the basis of ensuring good welding performance, the silver content of the solder should be as high as possible to avoid significantly affecting the overall color of the silver jewelry.

[0026] (3) Solder is formulated through the synergistic effect of multi-element alloying to achieve an optimized match of welding performance, physical properties, chemical properties and mechanical properties. Alloying can make the solder have better wettability and gap filling properties to the base material, but excessive alloying will cause complex interfacial reactions, which will lead to changes in the flow point temperature, corrosion of the base material, or formation of brittle compounds. Therefore, the selection of alloying elements and the amount added should be conducive to wettability without increasing corrosion of the base material.

[0027] (4) The solder has little color difference from the pure silver substrate, and the passivation effect of the alloying elements gives it excellent corrosion resistance and anti-discoloration properties.

[0028] (5) The alloying elements used in the solder must be green and environmentally friendly, do not produce toxic side effects, be inexpensive, and not contain precious elements.

[0029] The specific conceptual idea is as follows:

[0030] (1) High-temperature solder

[0031] High-temperature solder is used for the first or initial welding of workpieces and is the main load-bearing factor of wire products. The prepared high-temperature solder should have a high melting point, good fusion welding performance, high strength performance and excellent ductility, and the welded joint should be resistant to impact and vibration.

[0032] (2) Medium-temperature solder

[0033] Medium-temperature solder is used for intermediate welding stages of workpieces, usually involving one or more welding operations. It requires a melting point that is 60-80°C different from that of high-temperature solder, while also having a small melting temperature interval and good fusion welding performance.

[0034] (3) Low-temperature solder

[0035] Low-temperature solder is used for the final assembly welding of workpieces, which usually involves one or more welding operations. It requires that its melting point be 60-80°C different from that of medium-temperature solder, while the melting temperature interval of the content is small and the fusion welding performance is good.

[0036] Based on the above considerations, this invention optimizes the solder formulation for high-temperature, medium-temperature, and low-temperature welding, ensuring that the highest liquidus temperature of the solder does not exceed 910℃, the lowest solidus temperature is not lower than 670℃, and the welding temperature range is 60-80℃, providing good controllability. The purity of the high-temperature solder is not less than 93%, the medium-temperature solder not less than 80%, and the low-temperature solder not less than 65%, significantly reducing the risk of insufficient purity in wire-flanged products. The graded solder possesses excellent welding and corrosion resistance properties, a color close to pure silver, and can meet the preparation process and mechanical property requirements of different solder morphologies.

[0037] Furthermore, the total content of the unavoidable impurity elements does not exceed 0.1%.

[0038] Furthermore, the rare earth element is one or more of cerium, yttrium, lanthanum, neodymium, and gadolinium.

[0039] In the above materials, cerium is pure cerium with a content of 99.95 wt% or higher, yttrium is pure yttrium with a content of 99.95 wt% or higher, lanthanum is pure lanthanum with a content of 99.95 wt% or higher, neodymium is pure neodymium with a content of 99.95 wt% or higher, and gadolinium is pure gadolinium with a content of 99.95 wt% or higher.

[0040] Furthermore, the purity of high-temperature solder is not less than 93%, the purity of medium-temperature solder is not less than 80%, and the purity of low-temperature solder is not less than 65%.

[0041] Furthermore, the highest liquidus temperature of the solder does not exceed 910°C, the lowest solidus temperature is not lower than 670°C, and the welding temperature range is 60–80°C.

[0042] Furthermore, the liquidus temperature of the high-temperature solder is 885℃~905℃.

[0043] This invention sets the liquidus temperature of the high-temperature solder to 885℃~905℃. With a welding temperature calculated at a superheat of 15℃, there is a temperature difference of 40~60℃ between this solder and the melting point of pure silver. This ensures sufficient operating space during welding and prevents the substrate structure from melting and collapsing. To improve the solder's performance in terms of color matching, welding performance, processing performance, physical properties, and corrosion resistance, this invention utilizes multi-element alloying to achieve a synergistic effect. This results in a solder crystallization interval not exceeding 50℃, a color purity of over 93%, excellent welding and oxidation resistance, a color close to pure silver, and the ability to meet the preparation process and mechanical property requirements of different solder morphologies. After melting on the surface of the workpiece, the high-temperature solder exhibits a wetting angle of 20°~28°. Generally, a wetting angle less than 30° indicates good wetting; the smaller the contact angle, the better the wetting. Therefore, this solder exhibits excellent wetting properties with pure silver.

[0044] Furthermore, the liquidus temperature of the medium-temperature solder is 800℃~815℃, and the silver content of the medium-temperature solder is not less than 80%.

[0045] Furthermore, the liquidus temperature of the low-temperature solder is 700℃~715℃, and the silver content of the low-temperature solder is not less than 65%.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] The silver filigree jewelry graded welding solder of the present invention is set into three grades according to the welding temperature: high temperature, medium temperature and low temperature. The graded solder has excellent welding performance and corrosion resistance, its color is close to that of pure silver, and it can meet the preparation process and mechanical property requirements of different solder forms. Detailed Implementation

[0048] The present invention will now be further described in conjunction with specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0049] Example 1

[0050] A type of solder for graded welding of silver filigree jewelry includes high-temperature solder, medium-temperature solder and low-temperature solder. The high-temperature solder is used for the first or initial welding of the workpiece, the medium-temperature solder is used for intermediate welding after the workpiece is welded with high-temperature solder, and the low-temperature solder is used for the final assembly welding after the workpiece is welded with medium-temperature solder.

[0051] Among them, (1) the chemical composition of the high-temperature solder is: 0.3% copper, 3.3% zinc, 3.3% indium, 0.03% germanium, 0.05% tin, 0.01% cerium, the remainder being silver, and unavoidable impurities.

[0052] Testing revealed that the solder has a silver content exceeding 93%, a liquidus temperature of 901℃, a crystallization interval of 49℃, and exhibits good fluidity. It has a wetting angle of 25° with a pure silver substrate and achieves a brazing rate of over 95% within a 0.05mm weld gap. The color value L* is 92.5, the chromaticity a* value is -0.33, and the b* value is 3.9, indicating a minimal color difference compared to pure silver that is only perceptible to the naked eye. After immersing in artificial sweat at pH 6.5 for 8 hours, the solder shows a color change of approximately 3.2, similar to the sweat corrosion resistance of pure silver. The solder's microstructure is primarily a single-face-centered cubic structure, exhibiting excellent rolling and drawing properties, facilitating cold working into the required specifications. This solder can smoothly fill the weld seam at brazing temperatures of 915–925℃ without the risk of substrate corrosion.

[0053] (2) The chemical composition of the medium-temperature solder is: 19.5% copper, 0.15% zinc, 0.2% indium, 0.03% tin, 0.02% germanium, 0.01% cerium, the remainder being silver, and unavoidable impurities.

[0054] Testing revealed that the solder has a silver content exceeding 80%, a liquidus temperature of approximately 812℃, and a crystallization interval of approximately 47℃, exhibiting good fluidity. The solder's wetting angle with a pure silver substrate is 29°, indicating good wettability. The brazing rate within a 0.05mm weld joint is approximately 91%. After immersion in artificial sweat at pH 6.5 for 8 hours, the discoloration is significantly superior to traditional soldering fluxes. The annealed structure of this solder is a two-phase solid solution, exhibiting good cold working properties, and it is further ground into solder powder. This solder can smoothly fill the weld joint at brazing temperatures of 825–835℃ without the risk of high-temperature weld remelting or disintegration.

[0055] (3) The chemical composition of the low-temperature solder is: 20% copper, 13% zinc, 0.5% indium, 0.2% tin, 0.1% germanium, 0.01% yttrium, the remainder being silver, and unavoidable impurities.

[0056] Testing revealed that the solder has a silver content exceeding 66%, a liquidus temperature of approximately 705℃, and a crystallization interval of 25℃, exhibiting excellent fluidity. The wetting angle on a pure silver surface is approximately 31°, indicating good wettability to the silver substrate. The brazing rate within a 0.05mm weld joint is approximately 90%. After immersion in artificial sweat at pH 6.5 for 8 hours, the discoloration is significantly superior to traditional solders. The annealed structure of this solder is a two-phase solid solution, possessing good cold working properties, and it is further ground into solder powder. This solder can smoothly fill the weld joint at brazing temperatures of 720–725℃ without the risk of remelting or disintegration of the medium-temperature weld.

[0057] Example 2

[0058] A type of solder for graded welding of silver filigree jewelry includes high-temperature solder, medium-temperature solder and low-temperature solder. The high-temperature solder is used for the first or initial welding of the workpiece, the medium-temperature solder is used for intermediate welding after the workpiece is welded with high-temperature solder, and the low-temperature solder is used for the final assembly welding after the workpiece is welded with medium-temperature solder.

[0059] Among them, (1) the chemical composition of the high-temperature solder is: 0.1% copper, 3.9% zinc, 1% indium, 0.02% germanium, 0.95% tin, 0.01% cerium, 0.01% gadolinium, the remainder being silver, and unavoidable impurities.

[0060] Testing revealed that the solder has a silver content exceeding 94%, a liquidus temperature of 902℃, a crystallization interval of 44℃, and excellent fluidity. The solder's microstructure is primarily a single-face-centered cubic structure, exhibiting excellent rolling and drawing properties, facilitating cold working into solder materials of desired specifications. This solder can smoothly fill the weld seam at brazing temperatures of 915–925℃ without the risk of substrate corrosion.

[0061] (2) The chemical composition of the medium-temperature solder is: 18.55% copper, 0.95% zinc, 0.2% indium, 0.03% tin, 0.02% germanium, 0.01% yttrium, the remainder being silver, and unavoidable impurities.

[0062] Testing revealed that the solder has a silver content exceeding 80%, a liquidus temperature of approximately 812℃, and a crystallization interval of approximately 48℃, exhibiting good fluidity. The annealed structure of this solder is a two-phase solid solution, possessing good cold working properties, and it is further ground into solder powder. This solder can smoothly fill the weld seam at brazing temperatures of 825–835℃ without the risk of high-temperature weld remelting and disintegration.

[0063] (3) The chemical composition of the low-temperature solder is: 20.2% copper, 13.2% zinc, 0.5% indium, 0.5% tin, 0.2% germanium, 0.01% neodymium, the remainder being silver, and unavoidable impurities.

[0064] Testing revealed that the solder has a silver content exceeding 65%, a liquidus temperature of approximately 702°C, and a crystallization interval of 27°C, exhibiting excellent fluidity. The annealed structure of this solder is a two-phase solid solution, possessing good cold working properties, and it is further ground into solder powder. This solder can smoothly fill the weld seam at brazing temperatures of 722–725°C without the risk of remelting or disintegrating the weld seam at medium temperatures.

[0065] Example 3

[0066] A type of solder for graded welding of silver filigree jewelry includes high-temperature solder, medium-temperature solder and low-temperature solder. The high-temperature solder is used for the first or initial welding of the workpiece, the medium-temperature solder is used for intermediate welding after the workpiece is welded with high-temperature solder, and the low-temperature solder is used for the final assembly welding after the workpiece is welded with medium-temperature solder.

[0067] Among them, (1) the chemical composition of the high-temperature solder is: 4% zinc, 1.6% indium, 0.2% germanium, 0.2% tin, 0.01% cerium, 0.02% yttrium, the remainder being silver, and unavoidable impurities.

[0068] Testing revealed that the solder has a silver content close to 94%, a liquidus temperature of 900℃, a crystallization interval of 49℃, and exhibits good fluidity. The solder's microstructure is primarily a single face-centered cubic structure, providing excellent rolling and drawing properties, facilitating cold working into solder materials of desired specifications. This solder can smoothly fill the weld seam at brazing temperatures of 915–920℃ without the risk of substrate corrosion.

[0069] (2) The chemical composition of the medium-temperature solder is: 19.1% copper, 0.4% zinc, 0.4% indium, 0.02% tin, 0.01% germanium, 0.01% lanthanum, the remainder being silver, and unavoidable impurities.

[0070] Testing revealed that the solder has a silver content exceeding 80%, a liquidus temperature of approximately 813℃, and a crystallization interval of approximately 44℃, exhibiting good fluidity. The annealed structure of this solder is a two-phase solid solution, possessing good cold working properties, and it is further ground into solder powder. This solder can smoothly fill the weld seam at brazing temperatures of 825–835℃ without the risk of high-temperature weld remelting and disintegration.

[0071] (3) The chemical composition of the low-temperature solder is: 20.2% copper, 13.0% zinc, 0.7% indium, 0.3% tin, 0.05% germanium, 0.01% cerium, the remainder being silver, and unavoidable impurities.

[0072] Testing revealed that the solder has a silver content exceeding 65%, a liquidus temperature of approximately 705°C, and a crystallization interval of 26°C, exhibiting excellent fluidity. The annealed structure of this solder is a two-phase solid solution, possessing good cold-working properties, and it is further ground into solder powder. This solder can smoothly fill the weld seam at brazing temperatures of 720–725°C without the risk of remelting or disintegrating the weld seam at medium temperatures.

[0073] The following is a comparative example, as follows:

[0074] Comparative Example 1 (Changing the composition of high-temperature solder)

[0075] A type of silver filigree jewelry graded welding solder includes high-temperature solder, medium-temperature solder and low-temperature solder. The high-temperature solder is used for the first or initial welding of the workpiece, the medium-temperature solder is used for intermediate welding after the workpiece is welded with the high-temperature solder, and the low-temperature solder is used for the final assembly welding after the workpiece is welded with the medium-temperature solder; wherein, (1) the chemical composition of the high-temperature solder is: Copper 2.8% It contains 2.20% zinc, 0.01% indium, 0.01% germanium, 1.4% tin, 0.01% cerium, and the remainder is silver, as well as unavoidable impurities.

[0076] Testing revealed that the solder had a silver content exceeding 93%, a liquidus temperature of 901°C, a crystallization interval of 94°C, and significantly affected fluidity. The wetting angle with the pure silver substrate was 38°, and the brazing rate within a 0.05mm weld gap was only 83%. The color value L* was 90.5, the chromaticity a* value was 0.43, and the b* value was 4.07, a color difference from pure silver that was easily discernible to the naked eye. After soaking in artificial sweat with a pH of 6.5 for 8 hours, the solder showed a color change of approximately 5.4. Therefore, Comparative Example 1 is significantly inferior to the Example when used as a high-temperature solder.

[0077] (2) The chemical composition of the medium-temperature solder is: 19.5% copper, 0.15% zinc, 0.2% indium, 0.03% tin, 0.02% germanium, 0.01% cerium, the remainder being silver, and unavoidable impurities.

[0078] Testing revealed that the solder has a silver content exceeding 80%, a liquidus temperature of approximately 812℃, and a crystallization interval of approximately 47℃, exhibiting good fluidity. The solder's wetting angle with a pure silver substrate is 29°, indicating good wettability. The brazing rate within a 0.04mm weld joint is approximately 91%. After immersion in artificial sweat at pH 6.5 for 8 hours, the discoloration is significantly superior to traditional soldering fluxes. The annealed structure of this solder is a two-phase solid solution, exhibiting good cold working properties, and it is further ground into solder powder. This solder can smoothly fill the weld joint at brazing temperatures of 825–835℃ without the risk of high-temperature weld remelting or disintegration.

[0079] (3) The chemical composition of the low-temperature solder is: 20% copper, 13% zinc, 0.5% indium, 0.2% tin, 0.1% germanium, 0.01% yttrium, the remainder being silver, and unavoidable impurities.

[0080] Testing revealed that the solder has a silver content exceeding 66%, a liquidus temperature of approximately 705℃, and a crystallization interval of 25℃, exhibiting excellent fluidity. Its wetting angle on pure silver surfaces is approximately 36°, indicating good wettability to silver substrates. The brazing rate within a 0.04mm weld joint is approximately 90%. After immersion in artificial sweat at pH 6.5 for 8 hours, the discoloration is significantly superior to traditional solders. The annealed structure of this solder is a two-phase solid solution, possessing good cold working properties, and it is further ground into solder powder. This solder can smoothly fill weld joints at brazing temperatures of 720–725℃ without the risk of remelting or disintegration of the medium-temperature weld.

[0081] Comparative Example 2 (Changing the composition of medium-temperature solder)

[0082] A type of solder for graded welding of silver filigree jewelry includes high-temperature solder, medium-temperature solder and low-temperature solder. The high-temperature solder is used for the first or initial welding of the workpiece, the medium-temperature solder is used for intermediate welding after the workpiece is welded with high-temperature solder, and the low-temperature solder is used for the final assembly welding after the workpiece is welded with medium-temperature solder.

[0083] Among them, (1) the chemical composition of the high-temperature solder is: 0.3% copper, 3.3% zinc, 3.3% indium, 0.03% germanium, 0.05% tin, 0.01% cerium, the remainder being silver, and unavoidable impurities.

[0084] Testing revealed that the solder has a silver content exceeding 93%, a liquidus temperature of 901℃, a crystallization interval of 49℃, and exhibits good fluidity. It has a wetting angle of 27° with a pure silver substrate and achieves a brazing rate of over 95% within a 0.05mm weld gap. The color value L* is 92.5, the chromaticity a* value is -0.33, and the b* value is 3.9, with a slight color difference from pure silver that is perceptible to the naked eye. After immersing in artificial sweat at pH 6.5 for 8 hours, the solder shows a color change of approximately 3.2, demonstrating better resistance to sweat corrosion than pure silver. The solder's microstructure is primarily a single-face-centered cubic structure, exhibiting excellent rolling and drawing properties, facilitating cold working into the required specifications. The solder can smoothly fill the weld seam at brazing temperatures of 915–925℃ without the risk of substrate corrosion.

[0085] (2) The chemical composition of the medium-temperature solder is: Copper 11% It contains 2% zinc, 0.2% indium, 0.03% tin, 1% germanium, 0.05% cerium, and the remainder is silver, as well as unavoidable impurities.

[0086] Testing revealed that the solder had a silver content exceeding 80%, a liquidus temperature of approximately 844°C, a crystallization interval of approximately 129°C, and relatively poor fluidity. The wetting angle between the solder and the pure silver substrate was 36°, and the brazing rate within the weld was only about 80%. Furthermore, the solder's low solidus temperature severely limited the operational space for low-temperature soldering. The solder's color was significantly more reddish-yellow than pure silver, and the weld exhibited inconsistent color gradations. After soaking in artificial sweat with a pH of 6.5 for 8 hours, the surface showed a slight discoloration, appearing darker yellow or light brown. Therefore, the welding effect of this comparative example as a medium-temperature solder was significantly inferior to that of the example.

[0087] (3) The chemical composition of the low-temperature solder is: 20% copper, 13% zinc, 0.5% indium, 0.2% tin, 0.1% germanium, 0.01% yttrium, the remainder being silver, and unavoidable impurities.

[0088] Testing revealed that the solder has a silver content exceeding 66%, a liquidus temperature of approximately 705℃, and a crystallization interval of 25℃, exhibiting excellent fluidity. Its wetting angle on pure silver is approximately 36°, indicating good wettability to the silver substrate. The brazing rate within a 0.04mm weld joint is approximately 90%. After immersion in artificial sweat at pH 6.5 for 8 hours, the discoloration is slightly less than that of pure silver, but significantly superior to traditional soldering fluxes. The annealed structure of this solder is a two-phase solid solution, exhibiting good cold working properties, and it is further ground into solder powder. This solder can smoothly fill the weld joint at brazing temperatures of 720–725℃ without the risk of remelting or disintegration of the medium-temperature weld.

[0089] Comparative Example 3 (Changing the composition of the low-temperature solder)

[0090] A type of solder for graded welding of silver filigree jewelry includes high-temperature solder, medium-temperature solder and low-temperature solder. The high-temperature solder is used for the first or initial welding of the workpiece, the medium-temperature solder is used for intermediate welding after the workpiece is welded with high-temperature solder, and the low-temperature solder is used for the final assembly welding after the workpiece is welded with medium-temperature solder.

[0091] Among them, (1) the chemical composition of the high-temperature solder is: 0.3% copper, 3.3% zinc, 3.3% indium, 0.03% germanium, 0.05% tin, 0.01% cerium, the remainder being silver, and unavoidable impurities.

[0092] Testing revealed that the solder has a silver content exceeding 93%, a liquidus temperature of 901℃, a crystallization interval of 49℃, and exhibits good fluidity. It has a wetting angle of 27° with a pure silver substrate, and a brazing rate exceeding 95% within a weld gap of 0.05–0.06 mm. The color value L* is 92.5, the chromaticity a* value is -0.33, and the b* value is 3.9, with a slight color difference from pure silver that is perceptible to the naked eye. After soaking in artificial sweat at pH 6.5 for 8 hours, the solder shows a color change of approximately 3.2, demonstrating better resistance to sweat corrosion than pure silver. The solder's microstructure is primarily a single-face-centered cubic structure, exhibiting excellent rolling and drawing properties, facilitating cold working into the required specifications. The solder can smoothly fill the weld seam at brazing temperatures of 915–925℃ without the risk of substrate corrosion.

[0093] (2) The chemical composition of the medium-temperature solder is: 19.5% copper, 0.15% zinc, 0.2% indium, 0.03% tin, 0.02% germanium, 0.01% cerium, the remainder being silver, and unavoidable impurities.

[0094] Testing revealed that the solder has a silver content exceeding 80%, a liquidus temperature of approximately 812℃, and a crystallization interval of approximately 47℃, exhibiting good fluidity. The solder's wetting angle with a pure silver substrate is 29°, indicating good wettability. The brazing rate within a 0.04mm weld joint is approximately 91%. After immersion in artificial sweat at pH 6.5 for 8 hours, the discoloration is significantly superior to traditional soldering fluxes. The annealed structure of this solder is a two-phase solid solution, exhibiting good cold working properties, and it is further ground into solder powder. This solder can smoothly fill the weld joint at brazing temperatures of 825–835℃ without the risk of high-temperature weld remelting or disintegration.

[0095] (3) The chemical composition of low-temperature solder is as follows: Copper 17.5% It contains 12% zinc, 0.1% indium, 2.0% tin, 1.0% germanium, 0.01% yttrium, and the remainder is silver, as well as unavoidable impurities.

[0096] Testing revealed that the solder had a silver content exceeding 66%, a liquidus temperature of approximately 711°C, a solidus temperature of approximately 639°C, and a crystallization interval of 72°C. The solder exhibited poor fluidity, with a wetting angle of approximately 40° on pure silver surfaces. The brazing rate within weld seams with intervals of 0.04–0.06 mm was less than 70%. The solder color was noticeably yellowish-red and dark, and the weld seams were clearly visible. After immersion in artificial sweat with a pH of 6.5 for 8 hours, the color difference exceeded 6.5, indicating a significant yellowing and darkening. This solder carries a risk of cracking during cold working. Therefore, this comparative example is significantly inferior to the example when used as a low-temperature solder.

[0097] Comparative Example 4 (Traditional Welding Flux)

[0098] High-temperature, medium-temperature, and low-temperature solders were formulated using traditional red and yellow fluxes from the wire-threading process. The high-temperature solder was formulated using a traditional red flux formula, with a composition of 80% Ag, 18% Cu, and 2% Cd. The medium-temperature solder was formulated using traditional yellow flux, with a composition of 66% Ag, 18% Cu, 13% Zn, and 3% Cd. The low-temperature solder was formulated using traditional yellow flux, with a composition of 60% Ag, 20% Cu, 17% Zn, and 3% Cd.

[0099] The performance of traditional welding flux was tested and found to be as follows:

[0100] (1) The high-temperature grade welding flux has a brazing rate of 90-92% in the weld seam of 0.05-0.06mm. The color is a slightly yellowish white, which is quite different from the color of pure silver. After being soaked in sweat for 8 hours, the color difference is 6.4, and the discoloration is obvious. The flux has a purity of only 80% and contains the toxic element cadmium.

[0101] (2) The brazing rate of medium-temperature welding flux in the weld seam of 0.05-0.06mm is 90-93%. The color is a slightly yellowish and dark silver-white, which is significantly different from the color of pure silver. After being soaked in sweat for 8 hours, the color difference is 8.2, and the color change is obvious.

[0102] (3) The crystallization interval of the low-temperature welding flux is about 65℃. The brazing rate within a weld of 0.05-0.06mm is 91-93%. The color is silvery-gray with a yellow tint, and it is relatively dull. The color contrasts significantly with that of pure silver. After being soaked in sweat for 8 hours, the color difference is 10.4, and the discoloration is obvious.

[0103] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A solder for graded welding of silver filigree jewelry, characterized in that, It includes high-temperature solder, medium-temperature solder and low-temperature solder. The high-temperature solder is used for the first or initial welding of the workpiece. The medium-temperature solder is used for intermediate welding after the workpiece is welded with high-temperature solder. The low-temperature solder is used for the final assembly welding after the workpiece is welded with medium-temperature solder. The high-temperature solder comprises the following components by mass percentage: Copper 0–2.0%, zinc 0.01–5.0%, indium 0.01–3.0%, germanium 0.01–0.4%, tin 0.01–0.95%, rare earth elements 0.01–0.1%, the remainder being silver, and unavoidable impurity elements; Medium-temperature solder comprises the following components by weight percentage: Copper 18.0–19.5%, zinc 0.1–2.0%, indium 0.1–2.0%, tin 0.01–0.5%, germanium 0.01–0.5%, rare earth elements 0.01–0.1%, the remainder being silver, and unavoidable impurity elements; Low-temperature solder comprises the following components by weight percentage: Copper 18.0–21.0%, zinc 12.0–14.0%, indium 0.1–1.0%, tin 0.1–1.0%, germanium 0.01–0.5%, rare earth elements 0.01–0.1%, the remainder being silver, and unavoidable impurity elements.

2. The solder for graded welding of silver filigree jewelry according to claim 1, characterized in that, The rare earth element is one or more of cerium, yttrium, lanthanum, neodymium, and gadolinium.

3. The solder for graded welding of silver filigree jewelry according to claim 1, characterized in that, The purity of the high-temperature solder is not less than 93%, the purity of the medium-temperature solder is not less than 80%, and the purity of the low-temperature solder is not less than 65%.

4. The solder for graded welding of silver filigree jewelry according to claim 1, characterized in that, The highest liquidus temperature of the solder shall not exceed 910℃, the lowest solidus temperature shall not be lower than 670℃, and the welding temperature range shall be 60~80℃.

5. The solder for graded welding of silver filigree jewelry according to claim 4, characterized in that, The liquidus temperature of the high-temperature solder is 885℃~905℃.

6. The solder for graded welding of silver filigree jewelry according to claim 4, characterized in that, The liquidus temperature of the medium-temperature solder is 800℃~815℃, and the silver content of the medium-temperature solder is not less than 80%.

7. The solder for graded welding of silver filigree jewelry according to claim 4, characterized in that, The liquidus temperature of the low-temperature solder is 700℃~715℃, and the silver content of the low-temperature solder is not less than 65%.

8. The solder for graded welding of silver filigree jewelry according to claim 1, characterized in that, The total content of the unavoidable impurity elements does not exceed 0.1%.