A silver-based electrical contact wire preparation method

Abstract

The application discloses a silver-based electric contact wire preparation method, characterized in that the method is formed through hot extrusion, and comprises the following steps: (1) after sintering and re-pressing of a silver-based contact round ingot, the silver-based contact round ingot is loaded into a heating furnace for preheating before extrusion; (2) a pure silver coating snare is sprayed in the interior of an extrusion cylinder by means of a flame; (3) the heated silver-based contact round ingot is placed into the interior of the extrusion cylinder containing the pure silver coating snare, and is extruded into a wire, so that an extruded wire is obtained; and (4) the extruded wire is subjected to electrolysis to remove a silver layer on the surface of the wire, so that a silver-based contact wire with consistent inner and outer layer structures is obtained. The method enables the prepared silver-based electric contact wire to have continuous and uniform deformation capacity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrical contact material, in particular to a silver-based electrical contact wire rod preparation method with continuous and uniform deformation ability. BACKGROUND

[0002] The particle reinforced silver-based contact material refers to adding particle materials resistant to arc burning, melting welding, corrosion and oxidation to the silver matrix in order to enhance the mechanical and electrical properties of pure silver, and hot extrusion is the main processing method for particle reinforced silver-based contact material wire rod and sheet products. After the billet is heated at high temperature, it is then extruded. In the process of thermal deformation, the addition of hard reinforcing phase seriously hinders the plastic flow of the matrix, increases the deformation resistance, and is prone to sticking phenomenon, interface debonding, holes, cracks, residual material coating and other damages. Therefore, using extrusion lubrication can reduce the friction between the extruded material and the mold, reduce the unevenness of metal flow, thereby preventing or reducing the occurrence of cracks, and can also greatly reduce the extrusion pressure.

[0003] There are two common hot extrusion lubrication methods at present. One is to use a tool to dip a graphite-based lubricant such as graphite and grease coated on the inner wall of the tooling mold. The other is to use a glass lubricant. The glass lubricant contains inorganic silicon components, which has a high risk of entering the internal structure when in contact with the silver-based contact ingot during extrusion, and cannot meet the customer's requirements for Si content in electrical contacts. Therefore, it is not suitable for the production of silver-based contacts. The graphite-based lubricant cannot form a uniform mixture because the wettability of graphite in grease is poor, and the grease separates from the graphite after melting at high temperature. This results in discontinuous lubrication. Under the action of high temperature and high pressure during extrusion, the particle reinforced silver-based contact material has residual material in the area where the lubricant is insufficient on the inner wall of the extrusion cylinder. These residual materials are coated on the surface of the product during the extrusion of the next ingot, forming a non-uniform structure with loose bonding. This structure is prone to cracking, burrs and peeling abnormalities in subsequent processing.

[0004] In summary, there is an urgent need for a process to solve the problem of abnormal coating of foreign material structure on the surface of the wire rod caused by uneven extrusion lubrication, so as to obtain an electrical contact wire rod with uniform structure and continuous and uniform deformation ability. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings and deficiencies of the prior art, and to provide a silver-based electrical contact wire rod preparation method, which enables the prepared silver-based electrical contact wire rod to have continuous and uniform deformation ability.

[0006] To achieve the above-mentioned purpose, the technical solution of the present application is that the method is formed by hot extrusion, which includes the following steps:

[0007] (1) the silver-based contact round ingot is sintered, re-pressed, and then loaded into a heating furnace for preheating before extrusion;

[0008] (2) a pure silver coating snare is adopted in the interior of the extrusion cylinder by flame spraying;

[0009] (3) the heated silver-based contact round ingot is placed into the interior of the extrusion cylinder containing the pure silver coating snare, and is extruded into a wire, so that an extruded wire is obtained;

[0010] (4) the extruded wire is subjected to electrolysis to remove the silver layer on the surface of the wire, so that a silver-based contact wire with consistent inner and outer layer structures is obtained.

[0011] It is further provided that the silver-based electrical contact wire is a particle-reinforced silver-based composite material.

[0012] It is further provided that the thickness of the pure silver coating snare is 0.05-0.5% of the diameter of the silver-based contact round ingot.

[0013] It is further provided that the raw silver powder for the flame spraying is spherical, and the particle size range is 5-40 μm.

[0014] It is further provided that the flame spraying process parameters are as follows: spraying pressure 1-5 MPa, spraying distance 2-20 mm, powder feeding rate 15-50 g / min, oxygen flow rate 10-30 m 3 / h, and propane flow rate 0.5-10 m 3 / h.

[0015] It is further provided that the electrolysis process parameters of the extruded wire are as follows: electrolysis voltage 2.5-10 V, electrolysis current 300-1200 A, electrolysis mother liquor silver content 50-230 g / L, nitric acid concentration 2-15 g / L, and electrolysis time 2-20 min.

[0016] The innovative mechanism and beneficial effects of the present application are as follows:

[0017] First, a silver-based contact round ingot is prepared, the ingot is sintered and re-pressed, and then heated before extrusion; a pure silver coating of a certain thickness is adopted in the interior of the extrusion cylinder by flame spraying to replace the commonly used oil-based extrusion lubricant, and then the heated silver-based contact round ingot is placed into the interior of the extrusion cylinder for extrusion into a wire; the extruded wire is subjected to electrolysis to remove the silver layer on the surface of the wire, so that a material with consistent inner and outer layer structures is finally obtained, which is drawn to the required specification, and then cold upset to form a rivet-type electrical contact. The inner layer and the surface layer of the obtained material are uniformly consistent, and the deformation is continuous and uniform in all directions.

[0018] The traditional particle reinforced silver-based electric contact wire rod commonly uses graphite grease as the extrusion lubricant. Because of poor wettability between graphite and grease, the grease is separated from the graphite after being melted at high temperature, resulting in discontinuous lubrication effect. Thus, abnormal surface coating structure of the silver-based contact wire rod appears in the extrusion process, causing uneven deformation and cracking, peeling and other abnormalities in the subsequent rivet forming process. Compared with the prior art, the present application has the following characteristics: a certain thickness of pure silver coating is sprayed in the extrusion cylinder to replace the commonly used grease extrusion lubricant. In the flame spraying, the fuel and air are burned to produce high temperature, so that the silver powder particles are melted. At the same time, high pressure air passes through the Laval nozzle to generate high speed airflow, the melted silver powder particles are accelerated by the high speed airflow and impact on the surface of the extrusion cylinder to form a coating. The silver coating obtained by using this preparation process has uniform thickness and good combination with the extrusion cylinder. At a relatively high temperature, the silver layer is converted from solid state to semi-flowing or flowing state, forming a continuous, dense and ductile pressure-resistant film layer on the contact surface of the ingot and the die, which plays a lubricating role. This continuous and dense film layer prevents harmful gases in the atmosphere from entering during the whole hot working process, thereby preventing surface defects caused by residual oxide scale of the cylinder wall entering the extrusion deformation zone. At the same time, it plays a role in reducing the temperature drop of the billet during the transfer process and assisting lubrication during extrusion. The surface layer silver is removed in the subsequent extruded wire electrolysis process, so that the particle reinforced composite electric contact material with uniform structure is obtained. The material has consistent internal and external structure and exhibits excellent continuous deformation ability in the subsequent forming process. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to these drawings without creative labor.

[0020] Figure 1 Process flow chart of the present application.

[0021] Figure 2 Extruded wire and its edge local section metallographic structure diagram processed by the present application;

[0022] Figure 3 Extruded wire and its edge local section metallographic structure diagram processed by the traditional process. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the present application more clear, the following will further describe the present application in combination with the drawings.

[0024] Example one:

[0025] (1) Preparation of silver tin oxide (8) indium oxide (4) contact round ingot (i.e. 8wt% SnO2 particles, 4wt% In2O3 particles reinforced silver matrix material) with a diameter of 110 mm;

[0026] (2) After sintering and re-pressing, the round ingot is loaded into a heating furnace for preheating before extrusion;

[0027] (3) A pure silver coating snare is sprayed inside the extrusion cylinder by flame spraying, the coating thickness is 0.07% of the ingot diameter; the average particle size of the spherical silver powder used for spraying is 12 um, the spraying pressure is 3.8 MPa, the spraying distance is 5 mm, the powder feeding rate is 18 g / min; the oxygen flow is 12 m 3 / h, and the propane flow is 2.8 m 3 / h; the above gases are sprayed into high-speed airflow generated by a Laval nozzle;

[0028] (4) The heated silver matrix contact round ingot is placed inside the extrusion cylinder containing the pure silver coating snare, and is extruded into a wire;

[0029] (5) The extruded wire is subjected to electrolysis to remove the silver layer on the surface of the wire, and a silver matrix contact wire with consistent internal and external structures is obtained. The extruded wire electrolysis process is as follows: electrolysis voltage 8V, electrolysis current 327A, electrolyte silver content 62g / L, nitric acid concentration 8g / L, electrolysis time 18min.

[0030] Example Two:

[0031] (1) Preparation of silver cadmium oxide (12) contact round ingot (i.e. 12wt% CdO particles reinforced silver matrix material) with a diameter of 90 mm;

[0032] (2) After sintering and re-pressing, the round ingot is loaded into a heating furnace for preheating before extrusion;

[0033] (3) A pure silver coating snare is sprayed inside the extrusion cylinder by flame spraying, the coating thickness is 0.35% of the ingot diameter; the average particle size of the spherical silver powder used for spraying is 9 um, the spraying pressure is 3.6 MPa, the spraying distance is 12 mm, the powder feeding rate is 26 g / min; the oxygen flow is 21 m 3 / h, and the propane flow is 5.3 m 3 / h;

[0034] (4) The heated silver matrix contact round ingot is placed inside the extrusion cylinder containing the pure silver coating snare, and is extruded into a wire;

[0035] (5) The extruded wire is subjected to electrolysis to remove the silver layer on the surface of the wire, and a silver matrix contact wire with consistent internal and external structures is obtained. The extruded wire electrolysis process is as follows: electrolysis voltage 8V, electrolysis current 300-1000A, electrolyte silver content 190g / L, nitric acid concentration 12g / L, electrolysis time 7min.

[0036] Example Three:

[0037] (1) A silver-nickel (20) contact round ingot with a diameter of 105 mm was prepared (i.e., 20 wt% Ni particle reinforced silver matrix material);

[0038] (2) After sintering and re-pressing, the round ingot was loaded into an atmosphere heating furnace for preheating before extrusion;

[0039] (3) A pure silver coating collar was sprayed inside the extrusion cylinder using a flame spraying method, with a coating thickness of 0.25% of the ingot diameter; the spherical silver powder raw material used for spraying had an average particle size of 36 um, the spraying pressure was 4.2 MPa, the spraying distance was 17 mm, the powder feeding rate was 42 g / min; the oxygen flow rate was 16 m 3 / h, and the propane flow rate was 8 m 3 / h;

[0040] (4) The heated silver-based contact round ingot was placed inside the extrusion cylinder containing the pure silver coating collar, and was extruded into a wire;

[0041] (5) The extruded wire was subjected to electrolysis to remove the silver layer on the surface of the wire, thereby obtaining a silver-based contact wire with uniform internal and external structures. The electrolysis process for the extruded wire was as follows: electrolysis voltage 6 V, electrolysis current 842 A, electrolyte silver content 167 g / L, nitric acid concentration 9.8 g / L, and electrolysis time 12 min.

[0042] As shown in Figs. Figure 2 and Figure 3 , the surface of the extruded wire prepared by the conventional process is coated with an abnormal structure different from the bulk material. However, the surface and local structure of the extruded wire prepared by the process of the present patent are uniform.

[0043] Although the present application has been described with reference to several specific embodiments, it is understood that the present application is not limited to the specific embodiments disclosed. The present application is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A method for preparing silver-based electrical contact wire, characterized in that: This method involves hot extrusion molding and includes the following steps: (1) After sintering and repressing the silver-based contact ingots, they are preheated in a heating furnace before extrusion. (2) A pure silver coating ring is applied inside the extrusion cylinder by flame spraying; (3) The heated silver-based contact ingot is placed inside the extrusion cylinder containing a pure silver coated ring and extruded into wire to obtain extruded wire; (4) Electrolytically remove the silver layer on the surface of the extruded wire to obtain a silver-based contact wire with consistent inner and outer layer structure; The thickness of the pure silver coating ring is 0.05-0.5% of the diameter of the silver-based contact ingot; The silver powder used for flame spraying is spherical with a particle size range of 5-40 μm; The flame spraying process parameters are as follows: spraying pressure 1-5 MPa, spraying distance 2-20 mm, powder feeding rate 15-50 g / min; oxygen flow rate 10-30 m³ / min. 3 / h, propane flow rate 0.5-10 m 3 / h; The electrolysis process for extruded wire is as follows: electrolysis voltage 2.5-10V, electrolysis current 300-1200A, silver content of electrolytic mother liquor 50-230g / L, nitric acid concentration 2-15g / L, and electrolysis time 2-20min.

2. The method for preparing silver-based electrical contact wire according to claim 1, characterized in that: The silver-based electrical contact wire is a particle-reinforced silver-based composite material.

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