Cobalt starting sheet lug heating and riveting process

Abstract

The invention discloses a cobalt starting sheet lug heating and riveting process, belongs to the field of non-ferrous metallurgy, and solves the problems of easiness in cracking, large contact resistance and large heat affected zone of a welding process in cold riveting. The process comprises the following steps: processing a riveting hole in a cobalt starting sheet; the to-be-riveted area of the cobalt lug is locally heated, so that the temperature of the cobalt lug in the to-be-riveted area is increased to the phase change temperature of the cobalt lug; the heated cobalt lug in the hot state is conveyed to the riveting position of the cobalt starting sheet, and pressure is applied, so that the cobalt material softened through heating generates plastic flow and is filled into a riveting hole of the cobalt starting sheet, and a mechanically-interlocked riveting point is formed; and the pressure is kept until the riveting point is preliminarily shaped and then is relieved, and the cobalt lug piece shrinks in the cooling process, so that clamping force is generated at the joint. According to the method, the riveting area of the cobalt lug is softened through local heating, riveting is conducted through thermoplasticity of the cobalt lug, the microscopic cracks and cracking phenomena generated by cold riveting are thoroughly avoided, and the tensile strength and reliability of the connecting point are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal metallurgy, and specifically relates to a heating and riveting process for cobalt starter sheet lugs. Background Technology

[0002] In the cobalt electrolytic refining process, copper conductive lugs need to be securely connected to the cobalt starting electrode to form the cathode. Traditional connection methods include welding and cold riveting.

[0003] However, welding (such as arc welding and brazing) has drawbacks including a large heat-affected zone, easy deformation of thin starter sheets, potential introduction of impurities affecting cobalt purity, high energy consumption, and low efficiency. While cold riveting is more efficient, the high hardness and poor ductility of cobalt starter sheets at room temperature make direct riveting prone to generating micro-cracks around the riveting point, potentially even causing the starter sheet to crack. Furthermore, cold riveting results in insufficient mechanical contact area and high contact resistance, leading to overheating at the connection point when high-intensity electrolytic current is applied, wasting energy, and even causing connection failure, thus affecting the stable operation of the electrolytic cell. Summary of the Invention

[0004] The purpose of this invention is to provide a heating and riveting process for cobalt starter sheet lugs to solve the problems of easy cracking, high contact resistance, and large heat-affected zone in cold riveting.

[0005] The technical solution of this invention is: a heating and riveting process for cobalt starter sheet lugs, comprising the following steps: A. Feeding: Provide cobalt starter sheet and cobalt lugs, and machine rivet holes on the cobalt starter sheet at the positions where the cobalt lugs need to be installed; B. Local heating: Use a heating device to locally heat the area of ​​the cobalt lug to be riveted, so that the temperature of the cobalt lug in that area rises to its phase transition temperature; C. Pressure riveting: The heated cobalt lugs are sent to the riveting position of the cobalt starter sheet and pressure is applied by a pressure device, so that the heated and softened cobalt material plastically flows and fills the riveting hole of the cobalt starter sheet to form a mechanically interlocked riveting point. D. Pressure holding and cooling: Maintain pressure until the riveting point is initially shaped, then release the pressure to allow the workpiece to cool to room temperature. During the cooling process, the cobalt lugs will shrink, thereby generating a strong clamping force at the joint. Once the cobalt lugs have completely cooled, the riveting operation is complete.

[0006] As a further improvement of the present invention, in step B, the area of ​​the cobalt lug to be riveted is heated to 450°C to 750°C. This temperature range is much higher than the HCP to FCC phase transition temperature of cobalt (~417°C), ensuring that the cobalt is in a highly ductile state of face-centered cubic structure, while being much lower than its melting point (1495°C), avoiding the risk of excessive grain growth or melting.

[0007] As a further improvement of the present invention, in step B, a non-contact heating method is used to locally heat the area of ​​the cobalt ear piece to be riveted.

[0008] As a further improvement of the present invention, non-contact heating methods include heat treatment furnace heating, induction heating, laser heating, infrared heating, or isoelectric beam heating.

[0009] As a further improvement of the present invention, the laser heating uses a fiber laser or a disk laser, with a laser spot diameter of 1~5mm and a power of 500~3000W.

[0010] As a further improvement of the present invention, the heat treatment furnace includes resistance furnace, fuel furnace, induction furnace or vacuum furnace heating.

[0011] As a further improvement of the present invention, in step C, the applied pressure ranges from 10 to 50 kN, and the pressure holding time is from 0.5 to 3 seconds.

[0012] As a further improvement of the present invention, in step C, the pressure device includes a hydraulic press, a pneumatic press, or a servo-electric press.

[0013] The beneficial effects of this invention are: 1. High connection strength and no cracks: The cobalt lugs are softened by local heating and riveting by utilizing their thermoplasticity, which completely avoids the micro-cracks and cracking caused by cold riveting, and significantly improves the tensile strength and reliability of the connection point.

[0014] 2. Excellent electrical conductivity: The combined effects of high temperature and pressure break the oxide film on the material surface, enabling the cobalt lugs and the starting electrode to make large-area close contact, forming a physical connection with extremely low contact resistance, effectively reducing energy loss and the risk of local overheating during the electrolysis process.

[0015] 3. High production efficiency and high pass rate: The heating method used heats up quickly, the entire process cycle is short (usually within 10 seconds), it is easy to integrate into automated production lines, and the product consistency is good, with a significantly improved pass rate.

[0016] 4. No pollution and small heat-affected zone: It is a localized heat processing process, and the heat-affected zone is limited to the area around the riveting point at the millimeter level. It will not cause overall deformation of the cobalt lugs, and no third-party materials are introduced. This avoids the problem of weak weld points and weld point detachment contaminating the electrolyte, which can occur in welding processes, and effectively ensures the purity of cobalt products. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to specific embodiments.

[0019] Example 1 A cobalt starter plate ear piece heating and riveting process, such as Figure 1 As shown, it includes the following steps: A. Loading: Provide cobalt starter sheets and cobalt lugs. Machine rivet holes on the cobalt starter sheets at the locations where the cobalt lugs need to be installed. Clean the surfaces of the cobalt starter sheets and cobalt lugs to remove oxide layers and oil stains.

[0020] B. Localized Heating: Induction heating is used to locally heat the area of ​​the cobalt lug to be riveted, raising the temperature of the lug in that area to 450℃. The shape of the induction coil used matches the contour of the area of ​​the cobalt lug to be riveted.

[0021] C. Pressure riveting: The heated cobalt lugs are sent to the riveting position of the cobalt starter sheet and a pressure of 50kN is applied by a pneumatic press for 1 second. This causes the heated and softened cobalt material to plastically flow and fill the riveting hole of the cobalt starter sheet, forming a mechanically interlocked riveting point.

[0022] D. Pressure holding and cooling: Maintain pressure until the riveting point is initially shaped, then release the pressure to allow the workpiece to cool to room temperature in the air. During the cooling process, the cobalt lugs will shrink, thereby generating a strong clamping force at the joint. This is an important characteristic of heated riveting connections.

[0023] E. After the cobalt ear pieces have completely cooled, inspect the riveting quality.

[0024] Example 2 A process for heating and riveting cobalt starter sheet lugs includes the following steps: A. Loading: Provide cobalt starter sheets and cobalt lugs. Machine rivet holes on the cobalt starter sheets at the locations where the cobalt lugs need to be installed. Clean the surfaces of the cobalt starter sheets and cobalt lugs to remove oxide layers and oil stains.

[0025] B. Local heating: A fiber laser (laser spot diameter of 5mm and power of 3000W) is used to locally heat the area of ​​the cobalt lug to be riveted, so that the temperature of the cobalt lug in this area rises to 750℃.

[0026] C. Pressure riveting: The heated cobalt lugs are sent to the riveting position of the cobalt starter sheet and a pressure of 10kN is applied by a hydraulic press for 3 seconds. This causes the heated and softened cobalt material to plastically flow and fill the riveting hole of the cobalt starter sheet, forming a mechanically interlocked riveting point.

[0027] D. Pressure holding and cooling: Maintain pressure until the riveting point is initially shaped, then release the pressure to allow the workpiece to be cooled to room temperature by forced air cooling. During the cooling process, the cobalt lugs will shrink, thereby generating a strong clamping force at the connection.

[0028] E. After the cobalt ear pieces have completely cooled, inspect the riveting quality.

[0029] Example 3 A process for heating and riveting cobalt starter sheet lugs includes the following steps: A. Loading: Provide cobalt starter sheets and cobalt lugs. Machine rivet holes on the cobalt starter sheets at the locations where the cobalt lugs need to be installed. Clean the surfaces of the cobalt starter sheets and cobalt lugs to remove oxide layers and oil stains.

[0030] B. Local heating: The area to be riveted of the cobalt lugs is locally heated using a resistance furnace, raising the temperature of the cobalt lugs in that area to 600℃.

[0031] C. Pressure riveting: The heated cobalt lugs are sent to the riveting position of the cobalt starter sheet and a servo electric press is used to apply 40kN pressure for 0.5 seconds. This causes the heated and softened cobalt material to plastically flow and fill the riveting hole of the cobalt starter sheet, forming a mechanically interlocked riveting point.

[0032] D. Pressure holding and cooling: Maintain pressure until the riveting point is initially shaped, then release the pressure to allow the workpiece to be cooled to room temperature by forced air cooling. During the cooling process, the cobalt lugs will shrink, thereby generating a strong clamping force at the connection.

[0033] E. After the cobalt ear pieces have completely cooled, inspect the riveting quality.

[0034] This patent aims to solve the technical problems of easy cracking, high contact resistance, and excessive heat-affected zone in cold riveting processes. Small-scale tests have preliminarily verified the advantages of hot riveting in terms of contact tightness and crack resistance. The tests show that hot riveting is significantly better than cold riveting, especially in improving contact tightness and reducing the risk of cracking.

[0035] This invention provides a novel process for connecting cobalt starter tabs with high connection strength, good conductivity, high pass rate, and suitability for automated production. It can solve the problems of high hardness and poor ductility of cobalt metal, as well as the impact of welding on cobalt purity, thereby improving the purity of metal and the reliability of smelting in the metal refining process in the field of non-ferrous metal metallurgy.

Claims

1. A heating and riveting process for cobalt starter sheet lugs, characterized in that, Includes the following steps: A. Feeding: Provide cobalt starter sheet and cobalt lugs, and machine rivet holes on the cobalt starter sheet at the positions where the cobalt lugs need to be installed; B. Local heating: Use a heating device to locally heat the area of ​​the cobalt lug to be riveted, so that the temperature of the cobalt lug in that area rises to its phase transition temperature; C. Pressure riveting: The heated cobalt lugs are sent to the riveting position of the cobalt starter sheet and pressure is applied by a pressure device, so that the heated and softened cobalt material plastically flows and fills the riveting hole of the cobalt starter sheet to form a mechanically interlocked riveting point. D. Pressure holding and cooling: Maintain pressure until the riveting point is initially shaped, then release the pressure to allow the workpiece to cool to room temperature. During the cooling process, the cobalt lugs will shrink, thereby generating clamping force at the joint. Once the cobalt lugs have completely cooled, the riveting operation is complete.

2. The cobalt starter plate ear heating and riveting process according to claim 1, characterized in that: In step B, the area of ​​the cobalt ear piece to be riveted is heated to 450℃~750℃.

3. The cobalt starter plate ear heating and riveting process according to claim 2, characterized in that: In step B, a non-contact heating method is used to locally heat the area of ​​the cobalt ear piece to be riveted.

4. The cobalt starter plate ear heating and riveting process according to claim 3, characterized in that: Non-contact heating methods include heat treatment furnace heating, induction heating, laser heating, infrared heating, or isoelectric beam heating.

5. The cobalt starter plate ear-plate heating and riveting process according to claim 4, characterized in that: Laser heating uses fiber lasers or disk lasers with a laser spot diameter of 1~5mm and a power of 500~3000W.

6. The cobalt starter plate ear heating and riveting process according to claim 4, characterized in that: Heat treatment furnaces include resistance furnaces, fuel furnaces, induction furnaces, or vacuum furnaces.

7. The cobalt starter plate ear-plate heating and riveting process according to claim 1, characterized in that: In step C, the applied pressure ranges from 10 to 50 kN, and the pressure holding time is from 0.5 to 3 seconds.

8. The cobalt starter plate ear-plate heating and riveting process according to claim 7, characterized in that: In step C, the pressure equipment includes a hydraulic press, a pneumatic press, or a servo-electric press.

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