Method for producing silver tin oxide wire for rivet type contact

Abstract

This invention discloses a method for preparing silver-tin oxide wire for rivet-type contacts. The technical solution employs a bidirectional hot pressing process, which greatly improves the density of the ingot, resulting in near-fully dense finished wire. This improves the wire's plastic deformation capability and avoids cracking abnormalities caused by poor material density during subsequent rivet manufacturing. A low-hardness pure silver plating layer is formed by spraying onto the ingot surface, directly preventing the high-hardness silver-tin oxide layer from contacting the extrusion liner, extrusion die, extrusion nozzle, drawing die, and annealing fixture during hot extrusion, hot drawing, and annealing processes. This significantly improves the surface quality of the final finished wire, thereby mitigating cracking abnormalities during final rivet manufacturing. The hot spraying process forms a multi-layered composite material in the extruded wire: a low-hardness, easily machinable pure silver coating layer and an internal high-hardness, brittle AgSnO2 structure. This significantly reduces the fracture abnormalities that occur during subsequent hot drawing, improving the material yield.

Description

Technical Field

[0001] This invention belongs to the field of electrical contact material technology, specifically relating to a method for preparing silver tin oxide wire for rivet-type contacts that is easy to process and has high surface quality requirements. Background Technology

[0002] The alloy-containing silver-tin oxide material is widely used in automotive relays due to its good anti-adhesion and anti-DC material transfer properties. However, as automotive relays develop towards high-performance directions such as high load, high power, miniaturization, and high reliability, more stringent requirements are inevitably placed on electrical contact materials. The contact wires for riveting type must have high surface quality and good riveting performance to ensure that no cracking occurs during the riveting contact process (because cracks in the contacts are prone to trapping foreign objects and causing the base copper to deform at the transition R position, which seriously restricts the stability of the contact's electrical life).

[0003] The main problem with existing alloy-coated silver-tin oxide wire in rivet manufacturing is cracking. The main causes of cracking are the relatively poor density of the material itself and the poor surface quality of the finished wire. The poor surface quality is mainly due to the presence of powdery iron and chromium oxide particles, resulting in abnormal appearances such as black spots and lines visible to the naked eye. Therefore, the production of alloy-coated silver-tin oxide wire usually presents the following two problems: 1) Due to the small size of the oxide particles and the high hardness of the material, conventional cold pressing processes cannot press high-density silver-tin oxide ingots, affecting the density of the finished wire and ultimately leading to significant cracking during rivet upsetting; 2) Currently, the heating method for the internally oxidized silver-tin oxide ingots in the extrusion and drawing annealing processes is air heating at high temperatures. Under the long-term action of high-temperature air, the tooling and dies (such as extrusion liners, extrusion dies, material boats, and annealing tooling) are easily oxidized, producing powdery black iron and chromium oxides. During the extrusion process, the friction and wear between the internal silver oxide and tin oxide, which have a strong work-hardening effect, and the extrusion liner, die, and nozzle are significant. This causes powdery black iron and chromium oxide foreign particles from the surfaces of the liner, die, and nozzle to be introduced onto the surface of the extruded wire. During drawing and annealing, the direct contact between the silver oxide layer and the tooling surface also leads to the adhesion of powdery black iron and chromium oxide foreign particles to the wire surface. Ultimately, this results in poor appearance quality of the finished wire (visible color difference, black spots, and yellowing due to surface inclusions) and significant cracking during riveting.

[0004] Currently, the main research direction for silver tin oxide materials both domestically and internationally is to improve the electrical properties of contact materials by adjusting the composition, trace additives, and preparation processes. However, there is still no good solution for improving the surface quality and punching performance of silver tin oxide wire for rivet-type contacts. Therefore, how to solve and improve the surface quality and punching performance of silver tin oxide wire for rivet-type contacts is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings and deficiencies of existing technologies and to provide a method for preparing silver tin oxide wire for rivet-type contacts. This method helps to solve the problems of surface quality and forging performance of silver tin oxide wire for rivet-type contacts.

[0006] To achieve the above objectives, the technical solution of the present invention is a method for preparing silver tin oxide wire for rivet-type contacts, comprising the following steps:

[0007] (1) Smelt, cast, turn, extrude, and cold draw silver ingots, tin ingots, indium ingots, and additives to the specified specifications and perform internal oxidation to obtain internally oxidized wire;

[0008] (2) The inner oxide filaments from step (1) are broken and cold-pressed into cylindrical spindles;

[0009] (3) The cylindrical ingot is subjected to bidirectional hot pressing to improve the density of the ingot;

[0010] (4) Metal spraying is performed on the surface of the hot-pressed ingot to form a low-hardness pure silver plating layer on the surface of the ingot.

[0011] (5) The surface-sprayed ingots are hot-extruded into wires, then hot-drawn to the specified semi-finished product specifications, and the surface silver layer is removed by pickling.

[0012] (6) The pickled semi-finished filaments are finely drawn to the finished product specifications.

[0013] The silver tin oxide wire is further configured to have the following composition and content: silver content of 83% to 90% (wt.%), tin oxide content of 8% to 12% (wt.%), indium oxide content of 2.0% to 4.0% (wt.%), and additives that are elemental metals or alloys, consisting of one or more combinations of nickel, copper, antimony, and rare earth elements, with a total content ≤1.5% (wt.%).

[0014] The further setting is the cold drawing to the specified specification described in step (1). The internal oxidation process is carried out at 700–850℃, with an oxygen pressure of 0.6–1.5 MPa and an oxidation time of 25–120 h.

[0015] A further setting is that the diameter of the cylindrical spindle described in step (2) is:

[0016] The further setting is that the bidirectional hot pressing process in step (3) is as follows: the pressing equipment is a 315T~500T bidirectional four-column hydraulic press, the pressure is 20~25Mpa, the spindle heating temperature is 800~920℃, and the heating method is industrial frequency induction heating.

[0017] A further setting is that the thickness of the low-hardness pure silver plating in step (4) is 1.60 to 2.40 mm.

[0018] The further setting is that the metal sputtering process in step (4) includes:

[0019] a) will Pure silver metal wire is used as the plating metal wire. It passes through the nozzle and extends 10-20mm outside the air hood. Keep the spray gun as perpendicular to the substrate as possible. Set the spraying distance to 100-200mm and the spraying wire feeding speed to 3-6mm / s.

[0020] b) Ignition: Supply inert compressed gas to the spray gun, then turn on the oxygen and acetylene gas switches and ignite for spraying. During the spraying process, control the pressure of the inert compressed gas at 0.4-0.6 MPa, the oxygen pressure at 0.4-0.6 MPa, and the acetylene operating pressure at 0.05-0.2 MPa.

[0021] c) Spray coating: The moving speed of the spray gun is controlled at 200-350 mm / s to ensure that the thickness of a single layer of spray coating is controlled at 0.15-0.35 mm; in order to make the total thickness of the spray coating on the spindle meet the design requirements, the specific implementation method of spray coating is to use a 90° or 45° cross-layer spray coating method.

[0022] d) Shutdown: When the required number of coating layers is reached, stop wire feeding, turn off the oxygen and acetylene gas switches, and finally turn off the compressed air to end the coating process.

[0023] The further setting is that the extruded wire hot-drawing in step (5) to the specified semi-finished product specification has a diameter 0.3-0.6 mm larger than the diameter of the finished wire; the pickling process is as follows: the pickling medium is dilute sulfuric acid, and the acid density is 1.065-1.145 g / cm³. 3 The temperature is 60-80℃.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) By adopting a bidirectional hot pressing process, the density of the spindle is greatly improved, so that the finished wire material is nearly fully dense, which improves the plastic processing deformation ability of the wire material and avoids the abnormal cracking caused by poor material density in subsequent rivet making.

[0026] (2) By spraying a low-hardness pure silver coating on the surface of the ingot, the high-hardness silver tin oxide layer is directly prevented from contacting the extrusion liner, extrusion die, extrusion nozzle, drawing die and annealing tooling during hot extrusion, hot drawing and annealing. This prevents the introduction of powdery iron and chromium oxide particles formed by such tooling and die in the long-term air and high temperature environment into the surface of the silver tin oxide layer, thereby greatly improving the surface quality of the final finished wire and thus improving the abnormal cracking of the final rivet manufacturing.

[0027] (3) Through the thermal spraying process, the extruded wire is formed into a multi-layer composite material, namely a low-hardness, easy-to-process pure silver coating layer and a high-hardness, brittle AgSnO2 structure inside. This can significantly improve the abnormal fracture phenomenon that occurs in the subsequent hot drawing of the extruded wire and improve the yield of the material.

[0028] The silver tin oxide wire prepared by the process of this invention has high density and excellent surface quality (no black spots or lines caused by powdery iron oxide or chromium oxide inclusions on the surface), which greatly improves the cracking abnormalities that may occur during subsequent riveting. It has more obvious advantages in the field of preparing silver tin oxide wire for internal oxidation process and high oxide content riveting contacts. It can meet the relevant requirements of automotive relays to develop towards high performance such as high load, high power, miniaturization, and high reliability, and has broad application prospects. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0030] Figure 1 Flowchart of the fabrication process for the high oxide content silver tin oxide sheet contact of this invention;

[0031] Figure 2 Implementation Case - Schematic Diagram of the Extrusion Process;

[0032] Figure 3 Schematic diagram of the cross-section of the ingot after metal spraying;

[0033] Figure 4 Schematic diagram of the cross-section of the extruded wire. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0035] Example 1

[0036] A method for improving the surface quality and forging performance of silver tin oxide wire for rivet-type contacts comprises the following steps:

[0037] 1) Weigh out 22.332 kg of silver ingots, 2.202 kg of tin ingots, 0.862 kg of indium ingots, and 0.104 kg of copper ingots according to the weight percentage of Ag:SnO2:In2O3:CuO = 85.5:10:4:0.5 (single furnace smelting weight design is 25.5 kg). Melt, cast, turn, extrude, and cold draw the above raw materials in an induction furnace until… Internal oxidation is carried out at 720℃, with an oxygen pressure of 0.85 MPa and an oxidation time of 36 hours.

[0038] 2) The internally oxidized filaments are broken and cold-pressed on a four-column hydraulic press at a pressure of 20±2 MPa for a holding time of 10±1 s, to form a diameter... A cylindrical ingot.

[0039] 3) The cold-pressed cylindrical ingots are then subjected to medium-frequency induction heating in a medium-frequency induction heating furnace, with the ingot heating temperature controlled at 850±10℃. The heated ingots are then subjected to bidirectional pressing in a 400T bidirectional four-column hydraulic press at a pressure of 22MPa. Bidirectional hot pressing improves the density of the ingots before extrusion.

[0040] 4) The surface of the hot-pressed ingot is then metal-sprayed. Based on the design requirement of a 0.1mm coating thickness on the extruded wire surface, the thickness of the low-hardness pure silver plating after metal spraying is controlled at 1.6±0.2mm. The main implementation process of metal spraying is as follows: a) ... A) Using pure silver metal wire as the plating metal wire, the spray gun passes through the nozzle and extends 15±1mm beyond the air hood. The spray gun is kept as perpendicular to the substrate as possible. The spraying distance is set to 105±1mm and the wire feeding speed is 4±0.5mm / s. B) Ignition: Inert compressed gas is supplied to the spray gun, and then the oxygen and acetylene gas switches are turned on and ignition is performed. During the spraying process, the pressure of the inert compressed gas is controlled at 0.5±0.05Mpa, the oxygen pressure at 0.5±0.05Mpa, and the acetylene pressure at 0.01±0.02Mpa. C) Spraying: The moving speed of the spray gun is controlled at 230±2mm / s to ensure that the thickness of a single layer of spraying is controlled at 0.2±0.02mm. To ensure that the total thickness of the ingot spraying reaches the design requirements, the specific implementation method of spraying is to adopt a 90° layered spraying method. D) Shutdown: When the required number of spraying layers is reached, the wire feeding is stopped, the oxygen and acetylene gas switches are turned off, and finally the compressed air is turned off to end the spraying.

[0041] 5) The surface-sprayed ingots are hot-extruded into wires, and then hot-drawn to a diameter of... Specifications. The density is 1.08±0.01 g / cm³. 3 Dilute sulfuric acid solution: Heat the prepared dilute sulfuric acid solution to 65±1℃. [The text abruptly ends here.] The semi-finished silver tin oxide wire is acid-washed in an acid solution to remove the surface pure silver layer.

[0042] 6) Finely draw the pickled semi-finished filament to... Finished product specifications.

[0043] Example 2

[0044] 1) Weigh out 22.887 kg of silver ingots, 1.754 kg of tin ingots, and 0.859 kg of indium ingots according to the weight percentage ratio of Ag:SnO2:In2O3 = 88:8:4 (single furnace smelting weight design is 25.5 kg). Melt, cast, turn, extrude, and cold draw the above raw materials in an induction furnace until… Internal oxidation is carried out at 720℃, with an oxygen pressure of 0.6 MPa and an oxidation time of 30 hours.

[0045] 2) The internally oxidized filaments are broken and cold-pressed on a four-column hydraulic press at a pressure of 20±2 MPa for a holding time of 10±1 s, to form a diameter... A cylindrical ingot.

[0046] 3) The cold-pressed cylindrical ingots are then subjected to medium-frequency induction heating in a medium-frequency induction heating furnace, with the ingot heating temperature controlled at 850±10℃. The heated ingots are then subjected to bidirectional pressing in a 400T bidirectional four-column hydraulic press at a pressure of 22MPa. Bidirectional hot pressing improves the density of the ingots before extrusion.

[0047] 4) The surface of the hot-pressed ingot is then metal-sprayed. Based on the design requirement of a 0.1mm coating thickness on the extruded wire surface, the thickness of the low-hardness pure silver plating after metal spraying is controlled at 1.6±0.2mm. The main implementation process of metal spraying is as follows: a) ... A) Using pure silver metal wire as the plating metal wire, the spray gun passes through the nozzle and extends 15±1mm beyond the air hood. The spray gun is kept as perpendicular to the substrate as possible. The spraying distance is set to 105±1mm and the wire feeding speed is 4±0.5mm / s. B) Ignition: Inert compressed gas is supplied to the spray gun, and then the oxygen and acetylene gas switches are turned on and ignition is performed. During the spraying process, the pressure of the inert compressed gas is controlled at 0.5±0.05Mpa, the oxygen pressure at 0.5±0.05Mpa, and the acetylene pressure at 0.01±0.02Mpa. C) Spraying: The moving speed of the spray gun is controlled at 230±2mm / s to ensure that the thickness of a single layer of spraying is controlled at 0.2±0.02mm. To ensure that the total thickness of the ingot spraying reaches the design requirements, the specific implementation method of spraying is to adopt a 90° layered spraying method. D) Shutdown: When the required number of spraying layers is reached, the wire feeding is stopped, the oxygen and acetylene gas switches are turned off, and finally the compressed air is turned off to end the spraying.

[0048] 5) The surface-sprayed ingots are hot-extruded into wires, and then hot-drawn to a diameter of... Specifications. The density is 1.08±0.01 g / cm³. 3 Dilute sulfuric acid solution: Heat the prepared dilute sulfuric acid solution to 65±1℃. [The text abruptly ends here.] The semi-finished silver tin oxide wire is acid-washed in an acid solution to remove the surface pure silver layer.

[0049] 6) Finely draw the pickled semi-finished filament to... Finished product specifications.

[0050] Example 3

[0051] 1) Weigh out 22.566 kg of silver ingots, 1.759 kg of tin ingots, 0.97 kg of indium ingots, and 0.205 kg of yttrium ingots according to the weight percentage of Ag:SnO2:In2O3:Y2O3 = 86.5:8:4.5:1.0 (single furnace smelting weight design is 25.5 kg). Melt, cast, turn, extrude, and cold draw the above raw materials in an induction furnace until… Internal oxidation is carried out at 720℃, with an oxygen pressure of 0.6 MPa and an oxidation time of 30 hours.

[0052] 2) The internally oxidized filaments are broken and cold-pressed on a four-column hydraulic press at a pressure of 20±2 MPa for a holding time of 10±1 s, to form a diameter... A cylindrical ingot.

[0053] 4) The cold-pressed cylindrical ingots are then subjected to medium-frequency induction heating in a medium-frequency induction heating furnace, with the ingot heating temperature controlled at 850±10℃. The heated ingots are then subjected to bidirectional pressing in a 400T bidirectional four-column hydraulic press at a pressure of 22MPa. Bidirectional hot pressing improves the density of the ingots before extrusion.

[0054] 4) The surface of the hot-pressed ingot is then metal-sprayed. Based on the design requirement of a 0.1mm coating thickness on the extruded wire surface, the thickness of the low-hardness pure silver plating after metal spraying is controlled at 1.6±0.2mm. The main implementation process of metal spraying is as follows: a) ... A) Using pure silver metal wire as the plating metal wire, the spray gun passes through the nozzle and extends 15±1mm beyond the air hood. The spray gun is kept as perpendicular to the substrate as possible. The spraying distance is set to 105±1mm and the wire feeding speed is 4±0.5mm / s. B) Ignition: Inert compressed gas is supplied to the spray gun, and then the oxygen and acetylene gas switches are turned on and ignition is performed. During the spraying process, the pressure of the inert compressed gas is controlled at 0.5±0.05Mpa, the oxygen pressure at 0.5±0.05Mpa, and the acetylene pressure at 0.01±0.02Mpa. C) Spraying: The moving speed of the spray gun is controlled at 230±2mm / s to ensure that the thickness of a single layer of spraying is controlled at 0.2±0.02mm. To ensure that the total thickness of the ingot spraying reaches the design requirements, the specific implementation method of spraying is to adopt a 90° layered spraying method. D) Shutdown: When the required number of spraying layers is reached, the wire feeding is stopped, the oxygen and acetylene gas switches are turned off, and finally the compressed air is turned off to end the spraying.

[0055] 5) The surface-sprayed ingots are hot-extruded into wires, and then hot-drawn to a diameter of... Specifications. The density is 1.08±0.01 g / cm³. 3 Dilute sulfuric acid solution: Heat the prepared dilute sulfuric acid solution to 65±1℃. [The text abruptly ends here.] The semi-finished silver tin oxide wire is acid-washed in an acid solution to remove the surface pure silver layer.

[0056] 6) Finely draw the pickled semi-finished filament to... Finished product specifications.

[0057] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing silver tin oxide wire for rivet-type contacts, characterized in that... Includes the following steps: (1) Smelt, cast, turn, extrude, and cold draw silver ingots, tin ingots, indium ingots, and additives to the specified specifications and perform internal oxidation to obtain internally oxidized wire; (2) The inner oxide filaments from step (1) are broken and cold-pressed into cylindrical spindles; (3) The cylindrical ingot is subjected to bidirectional hot pressing to improve the density of the ingot; (4) Metal spraying is performed on the surface of the hot-pressed ingot to form a low-hardness pure silver plating layer on the surface of the ingot. (5) The surface-sprayed ingots are hot-extruded into wires, then hot-drawn to the specified semi-finished product specifications, and the surface silver layer is removed by pickling. (6) The pickled semi-finished filaments are finely drawn to the finished product specifications.

2. The method for preparing silver tin oxide wire for rivet-type contacts according to claim 1, characterized in that: The composition and content of the silver tin oxide wire are as follows: silver content is 83% to 90% (wt.%), tin oxide content is 8% to 12% (wt.%), indium oxide content is 2.0% to 4.0% (wt.%), and the additives are elemental metals or alloys, with one or more combinations of nickel, copper, antimony, and rare earth elements, and the total content is ≤1.5% (wt.%).

3. The method for preparing silver tin oxide wire for rivet-type contacts according to claim 1, characterized in that: The cold drawing to the specified specification described in step (1) is The internal oxidation process is carried out at 700–850℃, with an oxygen pressure of 0.6–1.5 MPa and an oxidation time of 25–120 h.

4. The method for preparing silver tin oxide wire for rivet-type contacts according to claim 1, characterized in that: The diameter of the cylindrical ingot mentioned in step (2) is:

5. The method for preparing silver tin oxide wire for rivet-type contacts according to claim 1, characterized in that: The bidirectional hot pressing process in step (3) is as follows: the pressing equipment is a 315T~500T bidirectional four-column hydraulic press, the pressure is 20~25Mpa, the spindle heating temperature is 800~920℃, and the heating method is industrial frequency induction heating.

6. The method for preparing silver tin oxide wire for rivet-type contacts according to claim 1, characterized in that: In step (4), the thickness of the low-hardness pure silver plating layer in metal sputtering is 1.60 to 2.40 mm.

7. The method for preparing silver tin oxide wire for rivet-type contacts according to claim 1, characterized in that: The metal sputtering process in step (4) includes the following: a) will Pure silver metal wire is used as the plating metal wire. It passes through the nozzle and extends 10-20mm outside the air hood. Keep the spray gun as perpendicular to the substrate as possible. Set the spraying distance to 100-200mm and the spraying wire feeding speed to 3-6mm / s. b) Ignition: Supply inert compressed gas to the spray gun, then turn on the oxygen and acetylene gas switches and ignite for spraying. During the spraying process, control the pressure of the inert compressed gas at 0.4-0.6 MPa, the oxygen pressure at 0.4-0.6 MPa, and the acetylene operating pressure at 0.05-0.2 MPa. c) Spray coating: The moving speed of the spray gun is controlled at 200-350 mm / s to ensure that the thickness of a single layer of spray coating is controlled at 0.15-0.35 mm; in order to make the total thickness of the spray coating on the spindle meet the design requirements, the specific implementation method of spray coating is to use a 90° or 45° cross-layer spray coating method. d) Shutdown: When the required number of coating layers is reached, stop wire feeding, turn off the oxygen and acetylene gas switches, and finally turn off the compressed air to end the coating process.

8. The method for preparing silver tin oxide wire for rivet-type contacts according to claim 1, characterized in that: The hot drawing of the extruded wire material to the specified semi-finished product size is 0.3-0.6 mm larger than the diameter of the finished wire material; the pickling process is as follows: the pickling medium is dilute sulfuric acid, the acid density is 1.065-1.145 g / cm 3 , and the temperature is 60-80℃.

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