Vacuum induction melting method of AlSn20Cu

Abstract

The invention discloses a vacuum induction melting method for AlSn20Cu, and relates to the technical field of aluminum alloy preparation. The method aims to solve the problems of high gas content, more inclusions, tin segregation and poor formability of cast ingots caused by traditional atmospheric smelting. The method comprises the following steps: preparing raw materials and a mold of a lining graphite pipe, and preheating; the pure aluminum, the AlCu50 intermediate alloy and the AlSn50 intermediate alloy are loaded in sequence; after vacuumizing, inert gas is filled, and furnace burden is melted through furnace baking and melting; after stirring and standing at 760 DEG C, cooling to 720 DEG C, and carrying out vacuum degassing refining; and finally, carrying out electrified casting to a mold at 700 DEG C under the vacuum degree of 2000-3000 Pa. According to the method, vacuum induction melting is combined with a specific graphite pipe lining mold, gas and inclusions are effectively reduced, the density and the structure uniformity of the cast ingot are improved, the process is simplified through process integration, and the obtained cast ingot is accurate in component and few in defect and meets the requirement of a high-performance sliding bearing material.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy preparation technology, specifically to a vacuum induction melting method for AlSn20Cu. Background Technology

[0002] AlSn20Cu is a bimetallic sliding bearing material with a high-strength aluminum-copper alloy matrix and a high content of soft tin phase dispersed throughout. Its core design concept utilizes the significant strengthening effect of copper on the aluminum matrix to achieve ultra-high fatigue strength, while the high tin content provides excellent friction reduction, compliance, and embedding properties. This perfect combination of soft and hard properties, coupled with good thermal conductivity, corrosion resistance, and relatively light weight, makes it the preferred material for main bearings and connecting rod bearings in modern high-performance internal combustion engines, especially diesel engines and high-power gasoline engines, and it is widely used in other high-load sliding bearing applications.

[0003] However, the industrial-scale smelting and preparation of this alloy faces significant challenges: traditional atmospheric smelting easily introduces gases and impurities, resulting in high gas content and numerous oxide inclusions in the ingots. Furthermore, the easy segregation and oxidation of tin makes ingot forming difficult, leading to internal defects such as shrinkage porosity and gas bubbles, severely affecting material consistency and service reliability. To improve smelting quality, vacuum induction melting technology has been applied to the preparation of various high-performance alloys. For example, Chinese invention patent CN116197361B discloses a vacuum induction melting and forming method for complex titanium-aluminum alloy components. This method aims to solve the problems of high melting point and poor fluidity of titanium-aluminum alloys through a series of complex pretreatments, including fabricating and coating a graphite shell with a high-temperature resistant ceramic coating, and performing vacuum degassing and gas washing. While this technical solution demonstrates the advantages of vacuum melting in improving the purity and filling capacity of molten metal, its process steps are cumbersome, and it is designed for titanium-aluminum high-temperature alloys. Furthermore, its specific coating and processing temperature may not be applicable to aluminum-tin-copper systems, and it cannot specifically solve the problems of gas and inclusion control, as well as formability issues in AlSn20Cu ingots.

[0004] Therefore, there is still a lack of a vacuum induction melting method in the existing technology that is specifically designed for the characteristics of AlSn20Cu alloy, can effectively simplify the process, and can ensure high purity and density of the ingot. Summary of the Invention

[0005] The purpose of this invention is to provide a vacuum induction melting method that achieves high purity and density of AlSn20Cu ingots by optimizing the preparation process of molds and casting, as well as the vacuum induction melting method, thereby avoiding problems such as high gas content, many impurities, and difficulty in forming caused by atmospheric melting.

[0006] The technical solution of this invention: A vacuum induction melting method for AlSn20Cu, comprising the following steps, Step 1: Prepare raw materials and molds. Prepare 40% AlSn50 master alloy, 2% AlCu50 master alloy, and 58% pure aluminum by weight percentage, and dry the raw materials. Prepare a metal casting mold with graphite tubes lined on the inner wall and preheat it. Step 2: Sequential loading. Add the prepared raw materials to the crucible of the vacuum induction furnace in the following order: first add all the pure aluminum, then add the AlCu50 master alloy, and finally add the AlSn50 master alloy on top of the material pile. Step 3: Vacuuming and melting. After evacuating the furnace chamber, inert gas is introduced to 20000±500 Pa. Then, the furnace charge is completely melted through the furnace drying and material melting stages. Step 4: Refining and degassing. After the melt temperature reaches 760℃±5℃, stir and let stand. Then cool the melt to 720℃±5℃. At this temperature, reduce the pressure in the furnace to 2000 Pa~3000 Pa for vacuum degassing and refining. After refining, let stand. Step 5: Casting. The refined melt is cooled to 700℃±5℃ and held at this temperature. Then, under a vacuum of 2000 Pa~3000 Pa, it is electro-cast into a mold with a graphite-lined tube to obtain AlSn20Cu ingots. Furthermore, in step 1, the preheating and baking conditions for the mold are to raise the temperature to 300°C and keep it at that temperature for 3 hours.

[0007] Furthermore, in step 2, the pure aluminum is in the form of waffle ingots, and both the AlCu50 master alloy and the AlSn50 master alloy are in the form of block materials.

[0008] Furthermore, the performance parameters of the graphite tube lining are: density 1.8–2.2 g / cm³, porosity 3%–9%, ​​thermal conductivity 6–10 W / (m·K), and coefficient of thermal expansion 3.2–3.8 × 10⁻ in the temperature range of 200℃–700℃. 6 / ℃.

[0009] Furthermore, in step 3, the furnace drying stage specifically involves drying the furnace for 10 minutes at a power of 15 kW in a cold furnace state; the material processing stage specifically involves increasing the power to 35 kW ± 1 kW for material processing.

[0010] Furthermore, in step 3, after the melt is completely melted, it is left to stand at 760°C for 3 minutes.

[0011] Furthermore, in step 3, the inert gas includes, but is not limited to, argon, and the pressure inside the furnace after filling is 20000 Pa.

[0012] Furthermore, in step 4, the stirring is a slow and uniform up-and-down stirring for 1 minute, followed by standing for 5 minutes.

[0013] Furthermore, the chemical composition of the AlSn20Cu ingot prepared by the method, by atomic percentage, is: 17.5%–22.5% tin, 0.7%–1.3% copper, with aluminum as the balance, and the remainder being unavoidable impurity elements, wherein the oxygen content of the impurity elements is ≤150 ppm. The beneficial effects of this invention are: (1) The AlSn20Cu ingot is cast in one piece by vacuum induction, which reduces the pollution of atmospheric gases during smelting.

[0014] (2) By using graphite tubes as mold liners for casting, the heat preservation and air permeability of the melt during solidification are ensured, and the formation of porosity defects inside the ingot and the uniformity of the ingot structure are reduced.

[0015] (3) The ingot has good forming quality. Through dissection and observation, there are no visible defects inside the ingot, which meets the aluminum alloy flaw detection standard.

[0016] (4) The AlSn20Cu ingot is cast in one piece by vacuum induction, which reduces the number of steps in the smelting process and integrates smelting and casting. This reduces the safety risks of energy consumption during transportation. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the product obtained in an embodiment of the present invention. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, it should not be construed that the scope of the subject matter of the present invention is limited to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0020] An AlSn20Cu vacuum induction casting ingot has the following specific composition: 17.5-22.5 at% tin, 0.7-1.3 at% copper, with aluminum as the balance at%, and the remainder being impurity elements, with an oxygen content ≤150 ppm.

[0021] In the preparation of vacuum induction casting ingots, tin is added in the form of AlSn2O, aluminum in the form of pure aluminum, and copper in the form of AlCu50 master alloy. The order of addition is as follows: pure aluminum block is placed at the bottom of the crucible, AlSn20 master alloy block is placed in the middle of the crucible, and AlCu50 master alloy block is placed at the top of the crucible.

[0022] The raw material preparation steps for an AlSn20Cu induction melting method are as follows: Step 1, Raw material preparation: Prepare raw materials according to the following mass percentage: 40% AlSn50 master alloy, 2% AlCu50 master alloy, and 58% pure aluminum.

[0023] Step 2, Melting preparation: Dry the raw materials prepared in Step 1 at 300℃ for 3 hours.

[0024] Step 3, mold preparation: Use a Φ145mm mold with a graphite tube lining inside, and bake at 300℃ for 3 hours. The properties of the graphite tube are: density 2±0.2g / cm3, porosity 6±3%, thermal conductivity 8±2W / m×k, and coefficient of thermal expansion (200℃~700℃) 3.5±0.3× 10-6 / ℃.

[0025] An induction melting method for AlSn20Cu includes the following steps: Step 1, Loading: First add pure aluminum, then AlCu50 master alloy, and finally add AlSn50 master alloy and place it on top of the crucible; Step 2, Vacuuming: After the machine is running normally, first evacuate it to the ultimate vacuum. Step 3, Gas filling: Fill with argon gas at 20000Pa once; Step 4, Furnace Drying: In a cold furnace state, first dry the furnace at 15kW for 10 minutes. Step 5, Material preparation: Increase power to 35kW±1kW for material preparation; Step 6, let stand: After the temperature reaches 760℃, stir slowly and evenly to prevent liquid from splashing. Stir for 1 minute, then let stand for 5 minutes. Step 7, Cooling down: Cool down to 720℃; Step 8, Degassing and Refining: The refining temperature is precisely controlled at 720℃±5℃, and a vacuum is drawn to 2000Pa~3000Pa. After completion, let it stand for 5 minutes. Step 9, Cooling: Cool down to 700℃; Step 10, heat preservation: Keep the temperature at 700℃ for 3 minutes to ensure uniform temperature; Step 11, casting: The casting temperature is 700℃, high-temperature electric casting, and the vacuum degree is 2000Pa~3000Pa.

[0026] Example: This example uses the preparation of a 20kg-grade AlSn20Cu induction casting ingot as an example. The specific implementation steps are as follows: Step 1, Raw material preparation: Prepare raw materials according to the required ratio of 8kg AlSn50 aluminum master alloy, 0.4kg AlCu50 aluminum master alloy, and 11.6kg pure Al blocks. Step 2, Melting preparation: Dry the raw materials prepared in Step 1 at 300℃ for 3 hours; Step 3, mold preparation: According to claim 5, use a Φ145mm mold with graphite paper lining inside, and bake at 300℃ for 3 hours. Step 4, loading: First add pure aluminum, then add AlCu50 master alloy, and finally add AlSn50 master alloy and place it on top of the crucible; Step 5, Vacuuming: After the machine is running normally, first evacuate it to the ultimate vacuum. Step 6, Gas filling: Fill with argon gas at 20000Pa once; Step 7, Furnace drying: In a cold furnace state, first dry the furnace at 15kW for 10 minutes; Step 8, Material preparation: Increase power to 35kW for material preparation; Step 9, let stand: After the temperature reaches 760℃, stir slowly and evenly to prevent liquid from splashing. Stir for 1 minute, then let stand for 5 minutes. Step 10, Cooling down: Cool down to 720℃; Step 11, Degassing and Refining: The refining temperature is precisely controlled at 720℃ and a vacuum of 2500Pa is drawn. After completion, let it stand for 5 minutes. Step 12, Cooling down: Cool down to 700℃; Step 13, heat preservation: Keep the temperature at 700℃ for 3 minutes to ensure uniform temperature; Step 14, casting: The casting temperature is 700℃, high-temperature electric casting, and the vacuum degree is 2500Pa; Step 15, unloading: Cool for more than 2 hours. After the ingot has completely cooled in a vacuum environment, disassemble the mold and remove the ingot.

[0027] Reference Figure 1 The obtained ingots were inspected. 50mm was removed from the head and 20mm from the tail of the circular ingot. No visible defects were found on the end faces. After vertically slicing the ingot in half, no visible defects were found on the cut surfaces.

[0028] The above provides a detailed description of the AlSn20Cu vacuum induction melting method provided by this invention. Specific examples have been used to illustrate the structure and working principle of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of this invention.

Claims

1. A vacuum induction melting method for AlSn20Cu, characterized in that: Includes the following steps, Step 1: Prepare raw materials and molds. Prepare 40% AlSn50 master alloy, 2% AlCu50 master alloy, and 58% pure aluminum by weight percentage, and dry the raw materials. Prepare a metal casting mold with graphite tubes lined on the inner wall and preheat it. Step 2: Sequential loading. Add the prepared raw materials to the crucible of the vacuum induction furnace in the following order: first add all the pure aluminum, then add the AlCu50 master alloy, and finally add the AlSn50 master alloy on top of the material pile. Step 3: Vacuuming and melting. After evacuating the furnace chamber, inert gas is introduced to 20000±500 Pa. Then, the furnace charge is completely melted through the furnace drying and material melting stages. Step 4: Refining and degassing. After the melt temperature reaches 760℃±5℃, stir and let stand. Then cool the melt to 720℃±5℃. At this temperature, reduce the pressure in the furnace to 2000 Pa~3000 Pa for vacuum degassing and refining. After refining, let stand. Step 5: Casting. The refined melt is cooled to 700℃±5℃ and held at this temperature. Then, under a vacuum of 2000Pa~3000Pa, it is electrically cast into a mold with a graphite-lined tube to obtain AlSn20Cu ingot.

2. The vacuum induction melting method for AlSn20Cu according to claim 1, characterized in that: In step 1, the preheating and baking conditions for the mold are to raise the temperature to 300°C and keep it at that temperature for 3 hours.

3. The vacuum induction melting method for AlSn20Cu according to claim 1, characterized in that: In step 2, the pure aluminum is in the form of waffle ingots, and both the AlCu50 master alloy and the AlSn50 master alloy are in the form of blocks.

4. The vacuum induction melting method for AlSn20Cu according to claim 1, characterized in that: The performance parameters of the graphite tube lining are as follows: density 1.8–2.2 g / cm³, porosity 3%–9%, ​​thermal conductivity 6–10 W / (m·K), and coefficient of thermal expansion 3.2–3.8 × 10⁻⁻ in the temperature range of 200℃–700℃. 6 / ℃.

5. The vacuum induction melting method for AlSn20Cu according to claim 1, characterized in that: In step 3, the furnace drying stage specifically involves drying the furnace for 10 minutes at a power of 15 kW in a cold furnace state; the material processing stage specifically involves increasing the power to 35 kW ± 1 kW for material processing.

6. The vacuum induction melting method for AlSn20Cu according to claim 1, characterized in that: In step 3, after the melt is completely melted, it is left to stand at 760°C for 3 minutes.

7. The vacuum induction melting method for AlSn20Cu according to claim 1, characterized in that: In step 3, the inert gas includes, but is not limited to, argon, and the pressure inside the furnace after filling is 20000 Pa.

8. The vacuum induction melting method for AlSn20Cu according to claim 1, characterized in that: In step 4, the stirring is a slow and uniform up-and-down stirring for 1 minute, followed by standing for 5 minutes.

9. The vacuum induction melting method for AlSn20Cu according to claim 1, characterized in that: The chemical composition of the AlSn20Cu ingot prepared by the method, by atomic percentage, is: 17.5%–22.5% tin, 0.7%–1.3% copper, with aluminum as the balance, and the remainder being unavoidable impurity elements, of which the oxygen content of the impurity elements is ≤150 ppm.

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