Silver or silver alloy cold composite copper rivet separation and recovery method

Abstract

The invention discloses a method for separating and recovering a silver or silver alloy cold composite copper rivet, which comprises the following steps of: firstly utilizing hydrogen and then utilizing oxygen in air at a high temperature to reduce the interface bonding force of silver or silver alloy and copper, and finally separating silver or silver alloy leftover materials and copper leftover materials by utilizing a roller. The method has the advantages that the silver or silver alloy cold composite copper rivets can be recycled, batch production can be achieved, use of chemical reagents is avoided, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the field of contact materials for low-voltage power distribution equipment, and in particular to a method for separating and recovering silver or silver alloy cold-compounded copper rivets. Background Art

[0002] In small and medium current relays, contactors, auxiliary switches, micro switches and other products, the electrical contact system is mainly composed of rivet contacts, especially double composite rivet contacts. Most of the double composite rivets are made by cold heading forming process. The silver-based material layer as the working layer and the copper as the base material are combined together by cold pressure welding. The double composite rivet electrical contacts are cold headed. There are some unqualified products in the production process of silver-copper rivets. Nearly 1,000 tons of silver alloy contact waste are generated in China every year. They are mainly recovered by chemical reagents, selectively dissolving silver, and passivating copper to achieve separation and recovery.

[0003] Patent CN1004882B invented a method for separating and recycling bimetallic silver-copper composite scraps. The main method is to heat the silver-copper composite scraps to 700-800 degrees Celsius in the air, keep the temperature constant for several hours, and then put the silver-copper composite scraps into water to cool. When heated at high temperature, the expansion coefficients of silver and copper are different. Oxygen invades between the bonding layers of silver and copper, causing the copper surface to oxidize. Then, by utilizing thermal expansion and contraction, the silver and copper separate by themselves. However, in the actual production process, silver-copper scraps, especially rivets, are made using cold heading forming technology. The copper surface and the silver surface are not flat surfaces, but a combination of concave and convex surfaces, and the self-separation of silver and copper cannot be achieved.

[0004] Patent CN112458289A invented a method for selectively separating and recovering silver from silver-nickel alloy copper-based rivet waste, which mainly involves placing the silver-nickel alloy copper-based rivets in a mixed solution of sulfuric acid, nitric acid and hydrogen peroxide, turning on ultrasonic vibration, and performing an acid dissolution reaction to dissolve the silver-nickel alloy while passivating the insoluble copper scraps. This invention uses a mixture of chemical reagents nitric acid and sulfuric acid, and after the rivets are recovered, a large amount of wastewater will be generated, and the cost of environmental protection treatment is high. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and provide a method for separating and recovering silver or silver alloy cold composite copper rivets. The method can effectively realize the separation and recovery method of silver or silver alloy composite copper rivets and realize batch production.

[0006] To achieve the above purpose, a method for separating and recovering silver or silver alloy cold composite copper rivets is provided, and its technical solution comprises the following steps:

[0007] S1. Mix silver or silver alloy cold-composite copper rivets with alumina powder and load them into a stainless steel boat, put the boat filled with rivets into a high-temperature furnace, and introduce hydrogen into the high-temperature furnace;

[0008] S2. After the high temperature furnace is heated up, turn off the hydrogen and introduce compressed air;

[0009] S3, cool the rivets heated at high temperature to room temperature and turn off the compressed air;

[0010] S4, putting the rivets into the drum, rolling and colliding with each other, and the silver or silver alloy scraps and alumina powder fall out of the drum from the gap of the drum and are separated from the copper scraps;

[0011] S5, separating the silver or silver alloy scraps and the alumina powder using a stainless steel sieve, and reusing the alumina powder in step S1;

[0012] S6. Smelt the silver or silver alloy scraps and then electrolyze them to purify the silver.

[0013] It is further configured that, in step S1, the temperature of the high temperature furnace is 100-500° C., and the air is introduced for 1-12 hours.

[0014] It is further configured that, in step S2, the temperature of the high temperature furnace is 600-820°C, and the rivet is in the high temperature furnace for 5-12 hours.

[0015] A further configuration is that in step S4, the roller is made of a stainless steel wedge-shaped slit mesh, and the slit width of the wedge-shaped slit mesh is 0.1-2 mm.

[0016] The innovative mechanism of the present invention is: first, the silver or silver alloy cold-compounded copper rivet is placed at high temperature in a hydrogen environment to achieve the hydrogen embrittlement of the metal. Hydrogen molecules will enter the metal dislocations, grain boundaries and precipitated phases, and at the same time penetrate into the gaps between the silver or silver alloy and the copper composite. Then, the oxygen in the air is combined with the hydrogen in the metal to oxidize the copper at the interface of the silver or silver alloy and the copper composite. Under the action of brittleness and oxidation, the mutual bonding force between the silver or silver alloy and the copper interface deteriorates. Finally, the rivets are tumbled by a roller, so that under the mutual squeezing and tumbling force between the rivets, the silver or silver alloy layer falls off the copper, and the silver or silver alloy layer and the aluminum oxide powder fall out of the roller from the gap in the roller, thereby achieving separation from the copper scrap.

[0017] The beneficial effects of the present invention are as follows: the recycling of silver or silver alloy cold composite copper rivets can realize batch production, avoid the use of chemical reagents, and reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying creative labor, other drawings obtained based on these drawings still belong to the scope of the present invention.

[0019] Figure 1 It is a schematic diagram of the process of the present invention;

[0020] Figure 2 Photograph of a silver or silver alloy cold-clad copper rivet before separation;

[0021] Figure 3 This is a photo of the silver alloy scrap after separation;

[0022] Figure 4 It is the copper scrap after separation. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail in the following examples.

[0024] Example 1

[0025] (1) Mixing silver-nickel alloy cold-composite copper rivets with alumina powder and loading them into a stainless steel boat, and placing the boat filled with rivets into a high-temperature furnace;

[0026] (2) Hydrogen is introduced into the high-temperature furnace, the furnace temperature is raised to 400°C, and after the heat preservation time is 5 hours, the hydrogen is turned off;

[0027] (3) Compressed air is introduced into the high-temperature furnace to raise the temperature to 800°C and keep the temperature for 5 hours;

[0028] (4) Cool the rivets that have been heated to high temperature to room temperature and turn off the compressed air;

[0029] (5) The rivets are placed in the drum and rolled to collide with each other, and the silver-nickel alloy scraps and alumina powder fall out of the drum from the gap in the drum and are separated from the copper scraps;

[0030] (6) The silver-nickel alloy scraps and alumina powder are separated by a stainless steel sieve, the alumina powder is reused, and the silver-nickel alloy scraps are smelted and then electrolyzed to purify silver.

[0031] Example 2

[0032] (1) Mixing the silver-tin oxide alloy cold-composite copper rivets with alumina powder and loading them into a stainless steel boat, and placing the boat filled with rivets into a high-temperature furnace;

[0033] (2) Hydrogen is introduced into the high-temperature furnace, the furnace temperature is raised to 500°C, and after the temperature is kept for 5 hours, the hydrogen is turned off;

[0034] (3) Compressed air is introduced into the high-temperature furnace to raise the temperature to 780°C and keep the temperature for 8 hours;

[0035] (4) Cool the rivets that have been heated to high temperature to room temperature and turn off the compressed air;

[0036] (5) The rivets are placed in the drum and rolled to collide with each other, and the silver-tin oxide alloy scraps and aluminum oxide powder fall out of the drum from the gap in the drum and are separated from the copper scraps;

[0037] (6) The silver-tin oxide alloy scraps and the alumina powder are separated by a stainless steel screen, the alumina powder is reused, and the silver-tin oxide scraps are melted and then electrolyzed to purify silver.

[0038] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for separating and recovering silver or silver alloy cold-compounded copper rivets, characterized in that The following steps are involved: S1. Mix silver or silver alloy cold-composite copper rivets with alumina powder and load them into a stainless steel boat, put the boat filled with rivets into a high-temperature furnace, and introduce hydrogen into the high-temperature furnace; S2. After the high temperature furnace is heated up, turn off the hydrogen and introduce compressed air; S3, cool the rivets heated at high temperature to room temperature and turn off the compressed air; S4, placing the rivets into a drum with a gap, the drum rolls to make the rivets collide with each other, and the silver or silver alloy scraps and alumina powder fall out of the drum from the gap of the drum and are separated from the copper scraps; S5, separating the silver or silver alloy scraps and the alumina powder using a stainless steel sieve, and reusing the alumina powder in step S1; S6. Smelt the silver or silver alloy scraps and then electrolyze them to purify the silver.

2. The method for separating and recovering silver or silver alloy cold composite copper rivets according to claim 1, characterized in that: In step S1, the temperature of the high temperature furnace is 100-500°C, and the hydrogen is introduced for 1-12 hours.

3. The method for separating and recovering silver or silver alloy cold composite copper rivets according to claim 1, characterized in that: In step S2, the temperature of the high temperature furnace is 600-820°C, and the rivets are in the high temperature furnace for 5-12 hours.

4. The method for separating and recovering silver or silver alloy cold composite copper rivets according to claim 1, characterized in that: In step S4, the roller is made of a stainless steel wedge-shaped slit mesh, and the slit width of the wedge-shaped slit mesh is 0.1-2 mm.

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