A method for preparing a low-gas-content silver plate

Abstract

The application specifically relates to a preparation method of a low-gas-content silver plate, comprising the following steps: S1, adding silver powder into a crucible to smelt into a silver liquid; S2, adding a blocky silver graphite solid into the silver liquid, the blocky silver graphite solid is dispersed into silver graphite powder at high temperature, the smelting temperature is reduced and heating is performed; S3, pouring the silver liquid into a mold, and cooling to obtain the silver plate. The blocky silver graphite scrap is used as a deoxidizer to remove oxygen in the molten silver liquid, one is that when the blocky silver graphite is placed on the surface of the high-temperature silver liquid, the blocky silver graphite is broken into silver graphite powder and covers the surface of the molten silver liquid, the silver graphite powder is in full contact with the silver liquid and continuously consumes oxygen in the silver liquid; two is that no impurity ions are introduced, and the purity of the silver plate is maintained; three is that the broken silver graphite powder of the blocky silver graphite scrap, since the graphite powder is micron-level or even nanometer-level powder, air gas is difficult to penetrate the silver graphite powder layer and enter the molten silver liquid, and further plays a role of air isolation.

Description

Technical Field

[0001] This invention belongs to the field of contact materials for low-voltage power distribution equipment, and specifically relates to a method for preparing a silver plate with low gas content. Background Technology

[0002] Silver graphite is widely used in circuit breakers for low-voltage electrical contacts, particularly for power line and motor protection. It exhibits excellent resistance to welding, high conductivity, and low, stable contact resistance. During the production of silver graphite products, scrap materials are inevitably generated, including extruded wires, extruded cakes, and discarded silver graphite contact parts.

[0003] Silver plates with low gas content can be processed into silver-based composite materials or into silver foil strips with low resistivity and no bubble defects, thus having wide applications in the production of contact materials.

[0004] Patent CN103658566 discloses a method for producing low-oxygen-content silver ingots. The method involves first adding charcoal or graphite particles to the bottom of a crucible, then adding silver powder for melting. A combustible material is then placed on the surface of the molten silver to prevent external oxygen from entering and to consume the oxygen already present in the molten silver. Finally, the molten silver is poured into a mold to produce low-oxygen-content silver ingots. However, in actual production, it has been found that combustible materials such as newspaper, coke powder, straw, or flour carbonize into lumps during combustion, resulting in insufficient contact area between the combustible material and the molten silver. Furthermore, combustible materials need to be continuously added during the oxygen removal process, but the later added materials do not actually contact the molten silver; instead, they cover the previously carbonized combustible material. This results in a poor actual oxygen removal effect, hindering widespread production. Currently, a new, efficient method for preparing low-oxygen-content silver ingots is urgently needed. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings and deficiencies of the existing technology and to provide a method for preparing a low-gas-content silver plate, comprising the following steps:

[0006] S1. Add silver powder to a crucible and melt it into liquid silver;

[0007] S2. Add solid silver graphite to the molten silver. The solid silver graphite disperses into silver graphite powder at high temperature. Reduce the melting temperature and heat.

[0008] S3. Pour the molten silver into a mold and cool it to obtain a silver plate.

[0009] Preferably, in step S1, the moisture content of the silver powder is less than 2%.

[0010] With this setup, due to the high moisture content, water vapor will be expelled from the silver powder during the high-temperature process, and air will enter the silver liquid through the remaining pores. This setup can further improve the degassing effect.

[0011] Preferably, in step S1, silver powder is continuously added to cover the surface of the molten silver during the smelting process.

[0012] This setup, by continuously adding silver powder, prevents air from entering the molten silver below, further enhancing the degassing effect.

[0013] Preferably, in step S2, the blocky silver graphite solid is dispersed into silver graphite powder at 1100-1200℃.

[0014] With this setup, since silver graphite is a powder metallurgy pressed and sintered product, after silver melts at 1100-1200℃, the loss of silver in the silver graphite will weaken the forming force between the silver powder and the graphite powder. The blocky silver graphite will break into silver graphite powder, which will cover the surface of the molten silver liquid. The silver graphite powder will be in full contact with the silver liquid, continuously consuming the oxygen in the silver liquid.

[0015] Preferably, in step S2, the blocky silver graphite solid includes one or more of the following: silver graphite extruded filament scrap, silver graphite extruded cake scrap, and silver graphite contact scrap.

[0016] Preferably, in step S2, the melting temperature is reduced to 1000-1050°C and heated for 10-15 minutes.

[0017] Preferably, in step S2, the heated silver liquid is heated to a higher temperature and covered with wood ash.

[0018] This setup allows the wood ash covering to block silver graphite powder or other graphite dust, preventing it from entering the silver plate during casting. Simultaneously, the wood ash prevents air from entering the molten silver, further reducing the gas content of the resulting silver plate. In practice, residual silver graphite powder can be gathered on the side away from the casting gate using a graphite rod. The portion of the molten silver near the casting gate is then covered with wood ash. The portion of the molten silver already covered with graphite powder does not require further covering with wood ash.

[0019] Preferably, the heated silver liquid is heated to 1100-1150℃ and heated for 1-2 minutes.

[0020] Preferably, in step S3, before casting, a layer of graphite is sprayed onto the contact area between the mold and the molten silver using acetylene combustion.

[0021] This setting creates a layer of graphite powder on the surface of the cast iron mold, making it easier for the silver plate to be demolded and preventing it from sticking to the cast iron mold and causing rust.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention innovatively uses blocky silver graphite scrap as a deoxidizer to remove oxygen from molten silver, offering the following advantages: First, when blocky silver graphite is placed on the surface of high-temperature molten silver, since silver graphite is a powder metallurgy pressed and sintered product, the loss of silver from the silver graphite after the silver melts at high temperatures weakens the forming force between the silver powder and graphite powder. The blocky silver graphite breaks into silver graphite powder, which covers the surface of the molten silver. The silver graphite powder is in full contact with the molten silver, continuously consuming the oxygen in the molten silver and generating carbon monoxide or carbon dioxide with low solubility, resulting in good deoxidation. At the same time, carbon monoxide or carbon dioxide precipitates from the molten silver and prevents external oxygen from entering. Second, it does not introduce impurity ions, maintaining the purity of the silver plate. Third, the silver graphite powder from the broken blocky silver graphite scrap, being micron- or even nano-sized powder, makes it difficult for gases in the air to penetrate the silver graphite powder layer into the molten silver, further isolating it from air. Attached Figure Description

[0024] 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.

[0025] Figure 1 This is a process flow diagram of the present invention;

[0026] Figure 2 This is an image of the silver strip made from a silver plate pressed into a silver strip, as shown in Comparative Example 1.

[0027] Figure 3 This is an appearance diagram of the silver strip made from the silver plate prepared in Example 1. Detailed Implementation

[0028] 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.

[0029] Example 1

[0030] (1) Add electrolytic silver powder into a crucible for melting. During the melting process, the silver powder is continuously melted into liquid silver, and silver powder is continuously added to cover the surface of the liquid silver to prevent the liquid silver from being exposed to the air.

[0031] (2) When the molten silver liquid is almost full of the crucible, add blocky silver graphite solid to the silver liquid. When the blocky silver graphite solid disperses into silver graphite powder at high temperature and completely covers the surface of the molten silver liquid, reduce the melting temperature to 1000-1050℃ and continue heating for 10-15 minutes.

[0032] (3) Melt the silver liquid and heat it to 1100-1150℃. After 1-2 minutes, use a graphite rod to gather the remaining silver graphite powder on the other side of the casting port. Cover the silver liquid on one side of the casting port with plant ash.

[0033] (4) Before casting, spray a layer of graphite with acetylene at the point where the mold contacts the molten silver, and then pour the molten silver into the mold. Remove the cooled silver plate from the mold, cut off the riser, and visually inspect for any holes that are not visible to the naked eye;

[0034] (5) Roll the low gas content silver plate into silver foil strip.

[0035] Comparative Example 1

[0036] (1) Add electrolytic silver powder into the crucible for melting. During the melting process, the silver powder continuously melts into liquid silver. Continue to add silver powder until the liquid silver fills the crucible.

[0037] (2) Stop adding silver powder for smelting, heat the molten silver to 1100-1150℃, and after 1-2 minutes, cover the molten silver with wood ash.

[0038] (3) Before casting, a layer of graphite is sprayed with acetylene at the position where the mold contacts the silver liquid. The silver liquid is then poured into the mold. The silver plate is cast quickly first and then slowly. The silver liquid fills the shrinkage cavities.

[0039] (4) Remove the cooled silver plate from the mold.

[0040] (5) Roll the silver plate into the silver foil strip.

[0041] The results of comparing the resistivity and appearance of Example 1 and Comparative Example 1 are shown in Table 1 below.

[0042]

[0043] 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 a low-gas-content silver plate, characterized in that, Includes the following steps: S1. Add silver powder to a crucible and melt it into liquid silver; S2. Add solid silver graphite to the molten silver. The solid silver graphite disperses into silver graphite powder at high temperature. Reduce the melting temperature and heat. S3. Pour the molten silver into a mold and cool it to obtain a silver plate.

2. The method for preparing a low-gas-content silver plate according to claim 1, characterized in that: In step S1, the moisture content of the silver powder is less than 2%.

3. The method for preparing a low-gas-content silver plate according to claim 1, characterized in that: In step S1, silver powder is continuously added to cover the surface of the molten silver during the smelting process.

4. The method for preparing a low-gas-content silver plate according to claim 1, characterized in that: In step S2, the bulk silver graphite solid is dispersed into silver graphite powder at 1100-1200℃.

5. The method for preparing a low-gas-content silver plate according to claim 1, characterized in that: In step S2, the blocky silver graphite solid includes one or more of the following: silver graphite extruded filament scraps, silver graphite extruded cake scraps, and silver graphite contact scraps.

6. The method for preparing a low-gas-content silver plate according to claim 1, characterized in that: In step S2, the melting temperature is reduced to 1000-1050℃ and heated for 10-15 minutes.

7. The method for preparing a low-gas-content silver plate according to claim 1, characterized in that: In step S2, the heated silver liquid is heated further and covered with wood ash.

8. The method for preparing a low-gas-content silver plate according to claim 7, characterized in that: Heat the heated silver solution to 1100-1150℃ and continue heating for 1-2 minutes.

9. The method for preparing a low-gas-content silver plate according to claim 1, characterized in that: In step S3, before casting, a layer of graphite is sprayed onto the contact area between the mold and the molten silver using acetylene combustion.

Images