Vacuum induction melting method of pure nickel cast ingot

Abstract

The invention discloses a vacuum induction melting method for a pure nickel cast ingot. The vacuum induction melting method comprises the steps that 1, raw material electrolytic nickel is placed in a vacuum induction furnace; 2, vacuumizing the vacuum induction furnace, stopping vacuumizing when the vacuum degree in the furnace reaches 15-20 Pa, filling argon into the vacuum induction furnace, and starting power transmission for smelting until the electrolytic nickel is completely molten; and 3, argon filling is stopped, the vacuum induction furnace is vacuumized till the vacuum degree in the furnace is 16-20 Pa, then the electrolytic nickel is refined in the vacuum atmosphere, and casting is completed. The argon is filled in the smelting process of the pure nickel cast ingot, so that a large amount of splashing caused by contact between molten electrolytic nickel metal liquid in the crucible and unmolten electrolytic nickel in the smelting process of the electrolytic nickel is eliminated, smelting accidents are avoided, and the stability of the smelting process is ensured.

Description

Technical Field

[0001] This invention belongs to the field of metal smelting technology, specifically relating to a vacuum induction melting method for pure nickel ingots. Background Technology

[0002] Currently, the main method for smelting pure nickel ingots in China is vacuum induction melting. In traditional vacuum induction melting, to remove oxygen from the raw material matrix and air from the melting environment, a high vacuum must be maintained throughout the entire melting process. This method typically requires the continuous operation of vacuum pumps such as mechanical pumps, Roots pumps, and booster pumps, resulting in high energy consumption. Furthermore, frequent operation increases maintenance difficulty and equipment failure rate. In addition, the vacuum environment and contact between hot and cold materials during melting can easily cause splashing. This splashing can lead to material adhesion at the top of the crucible, increasing the risk of bridging in electrolytic nickel and significantly impacting melting efficiency and product quality. To mitigate this effect, traditional melting methods involve slowly increasing the melting power, but this reduces the melting rate. Summary of the Invention

[0003] To address the aforementioned problems in the existing technology, this invention provides a vacuum induction melting method for pure nickel ingots. The technical problem to be solved by this invention is achieved through the following technical solution: A vacuum induction melting method for pure nickel ingots includes: Step 1: Place the raw material electrolytic nickel in a vacuum induction furnace; Step 2: Then, the vacuum induction furnace is evacuated. When the vacuum level inside the furnace reaches 15~20Pa, the evacuation is stopped, and argon gas is introduced into the vacuum induction furnace. Electricity melting is then started until the electrolytic nickel is completely melted. Step 3: Stop filling with argon gas and evacuate the vacuum induction furnace until the vacuum level inside the furnace is 16~20 Pa. Then, refine the electrolytic nickel and complete the casting under vacuum atmosphere.

[0004] Furthermore, in step 2, the pressure of the argon gas introduced into the vacuum induction furnace is 5000~8000 Pa.

[0005] Furthermore, in step 2, during the process of filling the vacuum induction furnace with argon gas, the melting power of the vacuum induction furnace is 80-93% of the rated power of the power supply equipment.

[0006] Furthermore, in step 1, the raw material electrolytic nickel is cut into cubes of 100~150×100×150mm and added to the vacuum induction furnace in batches. When adding the first batch directly to the crucible, the feeding is stopped when the crucible is 100~150mm away from the edge of the crucible. The remaining electrolytic nickel is added through the feeding hopper.

[0007] The beneficial effects of this invention are: 1. This invention eliminates the large amount of splashing caused by the contact between molten electrolytic nickel metal liquid and unmelted electrolytic nickel in the crucible during the melting process of pure nickel ingots by introducing argon gas, thereby avoiding melting accidents and ensuring the stability of the melting process. 2. In addition, the introduction of argon gas during the smelting process not only eliminates splashing but also enables high-power smelting, reducing the average smelting time of each ingot by 2-3 hours and increasing production efficiency by 18-20%. At the same time, the introduction of argon gas completely isolates external oxygen from entering the crucible, keeping the oxygen pressure inside the furnace under negative pressure and maintaining the tendency of oxygen elements inside the crucible to diffuse out of the furnace. Ultimately, the O and N element content of the ingot is controlled to within 50 ppm, ensuring product quality. 3. In addition, once the vacuum level inside the vacuum induction furnace reaches the specified requirements, the vacuum pumping equipment is shut down. Argon gas is then introduced to isolate external oxygen from entering the furnace, reducing the power consumption of each batch of ingots by about 8-12%, reducing the operating time of the vacuum pumping equipment, saving equipment operating costs, and indirectly reducing equipment maintenance costs. Detailed Implementation

[0008] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. Example 1

[0009] This invention provides a vacuum induction melting method for pure nickel ingots, taking a 4.5t capacity vacuum induction furnace as an example, specifically including: Step 1: Place the raw material electrolytic nickel in the crucible of the vacuum induction furnace.

[0010] Specifically, when there is too much raw material electrolytic nickel, it needs to be added in stages. First, it needs to be cut into 100~150×100×150mm cubes for easy feeding, and then placed into the crucible of the vacuum induction furnace. When adding the first batch directly to the crucible, stop feeding when it is about 100~150mm from the top edge of the crucible. The remaining electrolytic nickel is added through the feeding hopper and the furnace body is sealed.

[0011] Step 2: Then, the vacuum induction furnace is evacuated. When the vacuum level inside the furnace reaches 20 Pa, the evacuation is stopped, and argon gas is introduced into the vacuum induction furnace. Electricity is then supplied for melting until the electrolytic nickel is completely melted.

[0012] Vacuuming equipment such as mechanical pumps, Roots pumps, and booster pumps is used to evacuate the furnace body. Once the vacuum level inside the furnace reaches the set value, all vacuuming equipment is turned off, and argon gas is introduced into the furnace. The argon gas pressure inside the furnace is maintained at 8000 Pa. During the melting process of electrolytic nickel, this argon gas pressure is maintained, and the vacuuming equipment is not restarted. The melting power of the vacuum induction furnace is maintained at 85-93% of the rated power of the power supply equipment.

[0013] Throughout the entire electrolytic nickel melting process, the vacuum pumping equipment of the vacuum induction furnace, namely the mechanical pump, the Roots pump, and the booster pump, is shut down and no longer operates, saving energy consumption of the vacuum pumping equipment.

[0014] The purpose of first evacuating the furnace and then filling it with argon is to completely prevent external oxygen from entering the crucible and to maintain the oxygen pressure inside the vacuum induction furnace at a negative pressure state, ensuring the tendency of oxygen elements inside the crucible to diffuse out of the furnace and guaranteeing product quality.

[0015] By introducing argon gas, the excessive splashing caused by the molten metal in the crucible coming into contact with the unmelted electrolytic nickel was eliminated, thus preventing smelting accidents and ensuring the stability of the smelting process.

[0016] Furthermore, since vacuuming is not required during the electrolytic nickel melting process, the melting power of the vacuum induction furnace can be increased, thereby improving the melting efficiency of pure nickel.

[0017] Step 3: Stop filling with argon gas and evacuate the vacuum induction furnace until the vacuum level inside the furnace is 20 Pa. Then, refine the electrolytic nickel and complete the casting under vacuum atmosphere.

[0018] When multiple additions are made, since it takes a certain amount of time to turn on the vacuum equipment, the argon filling can be stopped when the last electrolytic nickel is added, and the mechanical pump, Roots pump and booster pump can be turned on in sequence to evacuate the vacuum induction furnace. This vacuum state is maintained until the electrolytic nickel casting process is completed.

[0019] The smelting time for this furnace of pure nickel ingots is 8.75 hours, the energy consumption of the equipment is reduced by about 8.2%, and the overall smelting efficiency is increased by more than 20%. Example 2

[0020] This invention provides a vacuum induction melting method for pure nickel ingots, taking a 4.5t capacity vacuum induction furnace as an example, specifically including: Step 1: Place the raw material electrolytic nickel in the crucible of the vacuum induction furnace.

[0021] Specifically, when there is too much raw material electrolytic nickel, it needs to be added in stages. First, it needs to be cut into 100~150×100×150mm cubes for easy feeding, and then placed into the crucible of the vacuum induction furnace. When adding the first batch directly to the crucible, stop feeding when it is about 100~150mm from the top edge of the crucible. The remaining electrolytic nickel is added through the feeding hopper and the furnace body is sealed.

[0022] Step 2: Then, the vacuum induction furnace is evacuated. When the vacuum level inside the furnace reaches 15 Pa, the evacuation is stopped, and argon gas is introduced into the vacuum induction furnace. Electricity is then supplied for melting until the electrolytic nickel is completely melted.

[0023] Vacuuming equipment such as mechanical pumps, Roots pumps, and booster pumps is used to evacuate the furnace body. Once the vacuum level inside the furnace reaches the set value, all vacuuming equipment is turned off, and argon gas is introduced into the furnace. The argon gas pressure inside the furnace is maintained at 5000 Pa. During the melting process of electrolytic nickel, this argon gas pressure is maintained, and the vacuuming equipment is not restarted. The melting power of the vacuum induction furnace is maintained at 80-85% of the rated power of the power supply equipment.

[0024] Throughout the entire electrolytic nickel melting process, the vacuum pumping equipment of the vacuum induction furnace, namely the mechanical pump, the Roots pump, and the booster pump, is shut down and no longer operates, saving energy consumption of the vacuum pumping equipment.

[0025] The purpose of first evacuating the furnace and then filling it with argon is to reduce the gas content inside the vacuum induction furnace. Maintaining the argon pressure at 5000Pa is to completely prevent external oxygen from entering the crucible and to maintain the oxygen pressure inside the vacuum induction furnace in a negative state, ensuring the tendency of oxygen elements inside the crucible to diffuse out of the furnace and guaranteeing product quality.

[0026] By introducing argon gas, the excessive splashing caused by the molten metal in the crucible coming into contact with the unmelted electrolytic nickel was eliminated, thus preventing smelting accidents and ensuring the stability of the smelting process.

[0027] Furthermore, since vacuuming is not required during the electrolytic nickel melting process, the melting power of the vacuum induction furnace can be increased, thereby improving the melting efficiency of pure nickel.

[0028] Step 3: Stop filling with argon gas and evacuate the vacuum induction furnace until the vacuum level inside the furnace is 15 Pa. Then, refine the electrolytic nickel and complete the casting under vacuum atmosphere.

[0029] When multiple additions are made, since it takes a certain amount of time to turn on the vacuum equipment, the argon filling can be stopped when the last electrolytic nickel is added, and the mechanical pump, Roots pump and booster pump can be turned on in sequence to evacuate the vacuum induction furnace. This vacuum state is maintained until the electrolytic nickel casting process is completed.

[0030] The smelting time for pure nickel ingots in this furnace has been reduced from 12 hours to 9.5 hours, the energy consumption of the equipment has been reduced by about 8%, and the overall smelting efficiency has been increased by more than 18%. Example 3

[0031] This invention provides a vacuum induction melting method for pure nickel ingots, taking a 4.5t capacity vacuum induction furnace as an example, specifically including: Step 1: Place the raw material electrolytic nickel in the crucible of the vacuum induction furnace.

[0032] Specifically, when there is too much raw material electrolytic nickel, it needs to be added in stages. First, it needs to be cut into 100~150×100×150mm cubes for easy feeding, and then placed into the crucible of the vacuum induction furnace. When adding the first batch directly to the crucible, stop feeding when it is about 100~150mm from the top edge of the crucible. The remaining electrolytic nickel is added through the feeding hopper and the furnace body is sealed.

[0033] Step 2: Then, the vacuum induction furnace is evacuated. When the vacuum level inside the furnace reaches 17 Pa, the evacuation is stopped, and argon gas is introduced into the vacuum induction furnace. Electricity is then supplied for melting until the electrolytic nickel is completely melted.

[0034] Vacuuming equipment such as mechanical pumps, Roots pumps, and booster pumps is used to evacuate the furnace body. Once the vacuum level inside the furnace reaches the set value, all vacuuming equipment is turned off, and argon gas is introduced into the furnace. The argon gas pressure inside the furnace is maintained at 6500 Pa. During the melting process of electrolytic nickel, this argon gas pressure is maintained, and the vacuuming equipment is not restarted. The melting power of the vacuum induction furnace is maintained at 83-90% of the rated power of the power supply equipment.

[0035] Throughout the entire electrolytic nickel melting process, the vacuum pumping equipment of the vacuum induction furnace, namely the mechanical pump, the Roots pump, and the booster pump, is shut down and no longer operates, saving energy consumption of the vacuum pumping equipment.

[0036] The purpose of first evacuating the furnace and then filling it with argon is to reduce the gas content inside the vacuum induction furnace. Maintaining the argon pressure at 6500Pa is to completely prevent external oxygen from entering the crucible and to maintain the oxygen pressure inside the vacuum induction furnace in a negative pressure state, ensuring the tendency of oxygen elements inside the crucible to diffuse out of the furnace and guaranteeing product quality.

[0037] By introducing argon gas, the excessive splashing caused by the molten metal in the crucible coming into contact with the unmelted electrolytic nickel was eliminated, thus preventing smelting accidents and ensuring the stability of the smelting process.

[0038] Furthermore, since vacuuming is not required during the electrolytic nickel melting process, the melting power of the vacuum induction furnace can be increased, thereby improving the melting efficiency of pure nickel.

[0039] Step 3: Stop argon gas filling and evacuate the vacuum induction furnace until the vacuum level inside the furnace is 17 Pa. Then, refine the electrolytic nickel and complete the casting under vacuum atmosphere.

[0040] When multiple additions are made, since it takes a certain amount of time to turn on the vacuum equipment, the argon filling can be stopped when the last electrolytic nickel is added, and the mechanical pump, Roots pump and booster pump can be turned on in sequence to evacuate the vacuum induction furnace. This vacuum state is maintained until the electrolytic nickel casting process is completed.

[0041] The smelting time for this furnace of pure nickel ingots is 9 hours, the energy consumption of the equipment is reduced by about 8%, and the overall smelting efficiency is increased by more than 19%.

[0042] The above method improves the smelting efficiency of pure nickel ingots by 18-20%. In large-scale, multi-furnace production, this invention can control the smelting time of each furnace of pure nickel ingots to within 9.5 hours, greatly improving smelting efficiency and reducing energy consumption by 8-12%, thereby reducing the production cost of each furnace of pure nickel ingots. Furthermore, the argon gas introduced isolates the molten metal from external gas, while maintaining the negative oxygen pressure inside the furnace, thus ensuring the outward diffusion of oxygen and guaranteeing product quality. This achieves improved production efficiency and reduced production costs without compromising the metallurgical quality of pure nickel ingots.

[0043] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for vacuum induction melting of pure nickel ingots, characterized in that, include: Step 1: Place the raw material electrolytic nickel in a vacuum induction furnace; Step 2: Then, the vacuum induction furnace is evacuated. When the vacuum level inside the furnace reaches 15~20Pa, the evacuation is stopped, and argon gas is introduced into the vacuum induction furnace. Electricity melting is then started until the electrolytic nickel is completely melted. Step 3: Stop filling with argon gas and evacuate the vacuum induction furnace until the vacuum level inside the furnace is 16~20 Pa. Then, refine the electrolytic nickel and complete the casting under vacuum atmosphere.

2. The vacuum induction melting method for pure nickel ingots according to claim 1, characterized in that, In step 2, the pressure of the argon gas introduced into the vacuum induction furnace is 5000~8000 Pa.

3. The vacuum induction melting method for pure nickel ingots according to claim 1 or 2, characterized in that, In step 2, during the process of filling the vacuum induction furnace with argon gas, the melting power of the vacuum induction furnace is 80-93% of the rated power of the power supply equipment.

4. The vacuum induction melting method for pure nickel ingots according to claim 1, characterized in that, In step 1, the raw material electrolytic nickel is cut into cubes of 100~150×100×150mm and added to the vacuum induction furnace in batches. When adding the first batch directly to the crucible, the feeding is stopped when the crucible is 100~150mm away from the edge of the crucible. The remaining electrolytic nickel is added through the feeding hopper.