Method for preparing pure regenerated high-temperature alloy raw material by using high-temperature alloy return scrap

Abstract

The invention provides a method for preparing a pure regenerated high-temperature alloy raw material by using high-temperature alloy return scraps. The method comprises the following steps: preparing materials, charging, smelting in an intermediate frequency furnace, deslagging, taking components and adding carbon, smelting in an AOD (Argon Oxygen Decarburization) furnace, taking components and pouring. Polluted high-temperature alloy return scraps with different steel grade components, different shapes and different specifications are refined through the intermediate frequency furnace and the AOD furnace to prepare the high-purity regenerated high-temperature alloy raw material, recycling of the high-temperature alloy return scraps is achieved, the raw material structure of the high-temperature alloy product is optimized, and the raw material cost of the high-temperature alloy product is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycling and remelting preparation of superalloy return materials, and specifically relates to a method for preparing pure recycled superalloy raw materials by using superalloy return materials. Background Art

[0002] Superalloys are widely used in the fields of aerospace, ground gas turbines for power generation, ships, nuclear power, ultra-supercritical thermal power generation, automobiles, petroleum, etc., and are mainly used as components such as turbine disks, turbine blades, rings, casings, shafts, fasteners, heat transfer tubes, etc.

[0003] In the field of aeroengines, since the utilization rate of superalloy materials is generally less than 10%, more than 90% of the raw materials become "waste materials". When the usage ratio of superalloy return materials is much lower than the ratio of return materials generated, the return materials generated in the process will be backlogged. At the same time, due to the lack of reasonable treatment processes for these return materials, they are often used as additive furnace charges for stainless steel smelting or discarded as waste materials, resulting in a large loss of precious metal elements.

[0004] Return materials generated during the smelting process, such as runner channels, pouring residues, ladle bottoms, bottom pads, turnings, risers, tails, etc., cut heads, cut tails, tong handles, cracked materials, turnings, etc. generated during the forging finishing process, and scrap materials, turnings, etc. generated during the forging process, all lead to a reduction in the utilization rate of superalloy materials. And the loss materials that appear in these production processes are collectively referred to as superalloy return materials. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the above deficiencies of the prior art, and provide a smelting process method for preparing pure recycled superalloy raw materials by using superalloy return materials. This method melts the superalloy return materials used as furnace charges into superalloy steel liquid by an intermediate frequency furnace, and then cooperates with an AOD furnace to purify the superalloy steel liquid prepared by the intermediate frequency furnace smelting, so as to prepare pure recycled superalloy raw materials.

[0006] The technical problem to be solved can be implemented by the following technical solutions.

[0007] A method for preparing pure recycled superalloy raw materials by using superalloy return materials is characterized by including the following technological steps:

[0008] (1) Batching and preparing materials;

[0009] (2) Loading materials;

[0010] (3) Intermediate frequency furnace smelting;

[0011] (4) Slag removal;

[0012] (5) Take the components and prepare carbon;

[0013] (6) AOD furnace smelting;

[0014] (7) Take the components and pour them.

[0015] Furthermore, in step (1),

[0016] The batching is based on the information of the inventory of high-temperature alloy recycled materials, including steel grades, specifications and shapes, combined with the main element composition requirements of the final required recycled high-temperature alloy raw material grade, to calculate the demand of high-temperature alloy recycled materials of different steel grades, specifications and shapes, and form a batching list for the medium-frequency furnace; the preparation of materials is the high-temperature alloy recycled materials and corresponding smelting auxiliary materials prepared according to the batching list of the medium-frequency furnace on site.

[0017] Furthermore, in step (2),

[0018] During the loading process, based on the actual proportions, shapes, and specifications of the high-temperature alloy return material, first, small-sized block materials are loaded into the bottom of the medium-frequency furnace, then, shavings and wood chips are placed on top of the small blocks, and finally, large blocks of high-temperature alloy return material are placed on top of the crucible.

[0019] Furthermore, in step (3),

[0020] After liquid steel appears in the crucible of the medium-frequency furnace, slag is formed and smelted by covering the surface of the high-temperature alloy steel with smelting auxiliary materials until the temperature in the furnace reaches ≥1700℃.

[0021] Furthermore, in step (4),

[0022] The slag removal process involves pouring all the high-temperature alloy steel liquid from the medium-frequency furnace into the tundish, moving the tundish to the slag removal station, using a slag removal rake to remove all the floating slag from the upper layer of the molten steel in the tundish, and then pouring the high-temperature alloy steel liquid back into the medium-frequency furnace.

[0023] Furthermore, in step (5),

[0024] The high-temperature alloy steel liquid returned to the intermediate frequency furnace after slag removal is subjected to composition analysis. Carbon addition is performed based on the C content in the steel liquid, and a carbon raiser is added to control the carbon content to the target value of 0.4-0.7%. The steel liquid is tapped when the temperature is controlled to be ≥1650℃, and the high-temperature alloy steel liquid is poured into the tundish.

[0025] Furthermore, in step (6),

[0026] The AOD furnace smelting process involves pouring all the high-temperature alloy steel liquid from the tundish into the AOD furnace for argon-oxygen decarburization and refining purification.

[0027] In the argon-oxygen decarburization process, based on the carbon content, a mixture of argon and oxygen is blown into the molten steel through the top lance and bottom side vents to raise the temperature of the molten steel to above 1700℃. The volume ratio of argon to oxygen in the mixture is 1:6 to 1:3. During the process, carbon samples are taken, and the decarburization operation ends when the carbon content reaches <0.05%, entering the reduction stage. Al blocks and Si powder are used to reduce the precious metal elements, including Cr and Nb, in the molten steel and slag. At the same time, lime and CaF2 are added for slag formation and desulfurization. The steel composition and temperature are adjusted during the reduction process.

[0028] Furthermore, in step (7),

[0029] After the reduction is completed in the AOD furnace smelting stage, a sample of the composition in the furnace is taken. If it meets the requirements of the main element and residual element composition of the recycled high-temperature alloy raw material, it is lifted out and poured. The lifting temperature is controlled at 1510~1580℃.

[0030] Among them, the residual element composition of the cast recycled high-temperature alloy raw materials shall meet the requirements of C<0.05%, Si<0.5%, Al<1.0% and Ti<0.8%, and the coarse and fine non-metallic inclusions of Class A, Class C and Ds shall be ≤0 grade, and the coarse and fine non-metallic inclusions of Class B and D shall be ≤0.5 grade.

[0031] This invention provides a refining process for melting high-temperature alloy recycled materials using a medium-frequency furnace and an AOD furnace, thereby preparing high-temperature alloy recycled materials of different compositions, shapes, and specifications into pure recycled high-temperature alloy raw materials for recycling in high-temperature alloy products.

[0032] The method of the present invention has the following beneficial effects: by refining contaminated high-temperature alloy return materials of different steel grades, shapes and specifications in a medium-frequency furnace and an AOD furnace, high-purity recycled high-temperature alloy raw materials are prepared, realizing the recycling of high-temperature alloy return materials, optimizing the raw material structure of high-temperature alloy products, and reducing the raw material cost of high-temperature alloy products. Detailed Implementation

[0033] The specific embodiments of the present invention will be further described in detail below.

[0034] This invention provides a method for preparing pure recycled high-temperature alloy raw materials from high-temperature alloy reclaimed materials, employing the following technical solution:

[0035] 1. Process Flow

[0036] Batching and preparation of materials → Charging → Induction furnace smelting → Slag removal → Composition and carbon addition → AOD furnace smelting → Composition and casting

[0037] 2. Specific technological measures

[0038] ① Batching and preparing materials:

[0039] Based on the information of the steel grades, specifications, shapes, etc. of the inventory superalloy return materials, combined with the main element composition requirements of the final required recycled superalloy raw material grades, calculate the demand for superalloy return materials of different steel grades, specifications, and shapes to form a batching list for the intermediate frequency furnace; at the same time, prepare superalloy return materials and corresponding melting auxiliary materials on-site according to the batching list of the intermediate frequency furnace. The superalloy return materials do not need to be processed.

[0040] ② Charging:

[0041] According to the actual batching and prepared shapes and specifications of the superalloy return materials, first load the small-sized block materials into the bottom of the intermediate frequency furnace, then cover the chip and shaving materials on top of the small block materials, and finally place the large-sized superalloy return materials on the upper part of the crucible.

[0042] ③ Intermediate frequency furnace melting:

[0043] After the intermediate frequency furnace loads and distributes materials in sequence according to the charging order, start to supply power for melting; after molten steel appears in the crucible of the intermediate frequency furnace, use melting auxiliary materials to cover the liquid surface of the metal superalloy steel for slag-making melting. During the melting process, use a thermocouple to measure the temperature. After the temperature in the furnace ≥ 1700 °C, the next step of slag removal can be carried out.

[0044] ④ Slag removal:

[0045] Pour all the superalloy steel liquid in the intermediate frequency furnace into the tundish, transfer the tundish to the slag removal station, and use a slag removal rake to completely remove all the floating slag on the upper layer of the tundish steel liquid. After slag removal, pour the superalloy steel liquid back into the intermediate frequency furnace.

[0046] ⑤ Taking composition and carbon addition:

[0047] After slag removal, the temperature of the superalloy steel liquid decreases. To ensure the melting temperature when entering the AOD furnace in the next step, pour the superalloy steel liquid after slag removal back into the intermediate frequency furnace and perform the operation of taking composition. According to the C element content in the steel liquid, perform the carbon addition operation, appropriately add a carburizer, and make the carbon element content reach the optimal target value of 0.4 - 0.7%. When the steel liquid temperature reaches ≥ 1650 °C, tap the steel, and pour the superalloy steel liquid into the tundish.

[0048] ⑥ AOD furnace melting:

[0049] After all the high-temperature alloy steel molten steel is poured into the AOD furnace, argon-oxygen decarburization and refining purification operations are carried out. Based on the carbon content, a mixture of argon and oxygen is blown into the molten steel through the top lance and bottom side tuyeres for decarburization. Through the reaction of C and O to generate CO2 and the secondary combustion of CO, the temperature of the molten steel is rapidly raised to above 1700℃. Simultaneously, the mixing ratio of argon and oxygen is adjusted according to the steel composition, typically between 1:6 and 1:3, to control the temperature and prevent it from becoming too high. During the process, a C sample is taken; when the C content reaches <0.05%, the decarburization operation ends, and the reduction stage begins. Al blocks and Si powder are used to reduce precious metal elements such as Cr and Nb in the molten steel and slag. At the same time, lime and CaF2 are added for slag formation and desulfurization. The steel composition and temperature are adjusted during the reduction process.

[0050] ⑦ Take the components and pour them:

[0051] After the reduction stage of the AOD furnace smelting is completed, a sample of the furnace composition is taken. If it meets the requirements for the main and residual element composition of the recycled high-temperature alloy raw material, it is hoisted out and cast. The hoisting temperature is controlled between 1510 and 1580℃. The residual element composition of the cast recycled high-temperature alloy raw material should meet the requirements of C < 0.05%, Si < 0.5%, Al < 1.0%, and Ti < 0.8%. The coarse and fine non-metallic inclusions of Class A, C, and Ds should be ≤ 0 grade, and the coarse and fine non-metallic inclusions of Class B and D should be ≤ 0.5 grade.

[0052] The technical solution of this invention has the following important features:

[0053] ① Slag removal operation after medium-frequency furnace melting. High-temperature alloy return materials consist of materials generated during the smelting process, such as runners, pouring residue, ladle bottoms, bottom pads, machining chips, caps, and tailings, as well as forging materials such as cut ends, tailings, clamp handles, cracked materials, and machining chips. These materials contain a large amount of impurities, including oil, contaminants, oxidation, and debris. After medium-frequency furnace melting, a large amount of slag will be generated on the surface of the molten steel, which is rich in inclusions and impurities. The purpose of the slag removal operation after medium-frequency furnace melting is to reduce the impact of slag on the composition, temperature, and purity of the molten steel during AOD furnace melting.

[0054] ② Carbon is added before tapping steel from the medium-frequency furnace. The purpose is to provide a reactant for the argon-oxygen decarburization operation in the AOD furnace. While ensuring the temperature of the molten steel, the CO and CO2 gases formed by the oxidation reaction carry the inclusions in the molten steel to the surface.

[0055] ③ The AOD furnace smelting and reduction process uses Al blocks and Si powder to reduce the molten steel, and promptly reduces precious metal elements such as Cr and Nb in the slag back to the high-temperature alloy steel, avoiding the loss of precious metals; at the same time, lime and CaF2 are added to slag formation and desulfurization, and the inclusions floating in the molten steel are adsorbed to improve the purity of the high-temperature alloy steel.

[0056] To further illustrate the effectiveness of the present invention, the present invention will be further described below with reference to specific embodiments.

[0057] Example 1

[0058] ① Ingredient preparation:

[0059] Based on the information on the steel grade, specifications, and shape of the recycled high-temperature alloy materials in the inventory, and combined with the main element composition requirements of the NiCrCoMo-1 grade of the final required recycled high-temperature alloy raw materials (Ni: 50%~65%, Cr: 15%~25%, Co: 5%~15%, Mo: 5%~15%), 5.5t of GH141 alloy blocks, 3.5t of GH738 alloy blocks, and 1t of GH141 alloy shavings are calculated to form the induction furnace batching list. The above-mentioned recycled high-temperature alloy materials do not require special treatment.

[0060] ② Loading:

[0061] Based on the actual batching, preparation, shape, and specifications of the high-temperature alloy return material, first, small-sized block materials are loaded into the bottom of the medium-frequency furnace, then, shavings are placed on top of the small blocks, and finally, large blocks of high-temperature alloy return material are placed on top of the crucible.

[0062] ③ Induction furnace smelting:

[0063] The medium-frequency furnace crucible has a capacity of 10 tons. According to the charging and distribution principle in step ②, the medium-frequency furnace is charged and power is supplied to start the melting process. After liquid steel appears in the medium-frequency furnace crucible, 300 kg and 280 kg of smelting auxiliary materials CaF2 and CaO are added to the surface of the high-temperature alloy steel liquid to cover and slag-forming smelting. Thermocouples are used to measure the temperature in the furnace. The measured temperature is 1710℃, and step ④, slag removal, can then be performed.

[0064] ④ Slag removal:

[0065] Pour all the high-temperature alloy steel liquid from the medium-frequency furnace into the tundish, move the tundish to the slag removal station, and use a slag remover to remove all the floating slag from the top of the molten steel in the tundish. After slag removal, pour the high-temperature alloy steel liquid back into the medium-frequency furnace.

[0066] ⑤ Take the components and prepare the carbon:

[0067] After slag removal, the temperature of the high-temperature alloy steel melt drops. To ensure the next step of entering the AOD furnace for smelting, the high-temperature alloy steel melt after slag removal is poured back into the medium-frequency furnace and its composition is taken. The carbon content in the steel melt is 0.25%. 15 kg of carbon raiser is added according to the target carbon content of 0.4%. The steel melt is heated and when the tapping temperature reaches 1680℃, the steel melt is poured into the tundish for tapping.

[0068] ⑥AOD furnace smelting:

[0069] The carbon content is 0.4%. A mixture of argon and oxygen is blown into the molten steel through the top lance and bottom side vents for decarburization. The argon-oxygen mixing ratio is 1:5. During the process, a carbon sample is taken, and the carbon content is 0.02%. The decarburization operation is completed. At this time, the temperature of the molten steel is 1750℃, and the Al content is 0.5%, the Ti content is 0.03%, and the Si content is 0.07%. The reduction stage begins. 78 kg of Al blocks and 48 kg of Si powder are added to the molten steel to reduce the precious metal element Cr in the molten steel and slag. 125 kg of CaO and 58 kg of CaF2 are added respectively for slag formation and desulfurization.

[0070] ⑦ Take the components and pour them:

[0071] After the reduction stage of the AOD furnace smelting process, a sample of the furnace composition was taken. The residual elemental composition of the recycled high-temperature alloy raw material was 0.04% C, 0.12% Si, 0.95% Al, and 0.03% Ti. The temperature of the molten steel was measured at 1540℃ before tapping. Electrode samples were taken after casting and tapping to detect the content of non-metallic inclusions, as shown in Table 1.

[0072] Example 2

[0073] Steps ② and ④ in this embodiment are the same as in embodiment 1. The other steps are as follows:

[0074] ① Ingredient preparation:

[0075] Based on the information regarding the steel grade, specifications, and shape of the recycled high-temperature alloy materials in the inventory, and combined with the main element composition requirements of the final required recycled high-temperature alloy raw material grade GH4169-1 (Ni: 50%–70%, Cr: 12%–24%, Nb: 1.5%–6%, Mo: 2%–10%), the following quantities are calculated: 1.2t of GH4169 alloy blocks, 0.7t of YZGH4169 alloy machined scrap, 0.5t of YZGH4169 alloy low-magnification physical and chemical test pieces, 0.3t of GH4169 alloy rolled bar scrap, and 2.3t of GH4169 alloy machined scrap. The above-mentioned recycled high-temperature alloy materials do not require special treatment in the medium-frequency furnace batching list.

[0076] ③ Induction furnace smelting:

[0077] The medium-frequency furnace crucible has a capacity of 5 tons. According to the charging and distribution principle in step ②, the medium-frequency furnace is charged and power is supplied to start the melting process. After liquid steel appears in the medium-frequency furnace crucible, 123 kg and 147 kg of smelting auxiliary materials CaF2 and CaO are added to the surface of the high-temperature alloy steel liquid to cover and slag it up for smelting. Thermocouples are used to measure the temperature in the furnace. The measured temperature is 1735℃, and step ④, slag removal, can then be performed.

[0078] ⑤ Take the components and prepare the carbon:

[0079] After slag removal, the temperature of the high-temperature alloy steel melt drops. To ensure the next step of entering the AOD furnace for smelting, the high-temperature alloy steel melt after slag removal is poured back into the medium-frequency furnace and its composition is taken. The carbon content in the steel melt is 0.12%. 21.5 kg of carbon raiser is added according to the target carbon content of 0.55%. The steel melt continues to be heated. When the tapping temperature reaches 1675℃, the steel melt is poured into the tundish for tapping.

[0080] ⑥AOD furnace smelting:

[0081] The carbon content is 0.55%. A mixture of argon and oxygen is blown into the molten steel through the top lance and bottom side vents for decarburization. The argon-oxygen mixing ratio is 1:4. During the process, a carbon sample is taken, with a carbon content of 0.05%. The decarburization operation is then completed. At this point, the temperature of the molten steel is 1780℃, and the Al content is 0.12%, Ti content is 0.01%, and Si content is 0.05%. The reduction stage begins. 50.5 kg of Al blocks and 23 kg of Si powder are added to the molten steel to reduce precious metal elements such as Cr and Nb in the molten steel and slag. 75 kg of CaO and 36 kg of CaF2 are added respectively for slag formation and desulfurization.

[0082] ⑦ Take the components and pour them:

[0083] After the reduction stage of the AOD furnace smelting process, a sample of the furnace composition was taken. The residual elemental composition of the recycled high-temperature alloy raw material was 0.03% C, 0.08% Si, 0.83% Al, and 0.01% Ti. The temperature of the molten steel was measured at 1570℃ before tapping. Electrode samples were taken after casting and tapping to detect the content of non-metallic inclusions, as shown in Table 1.

[0084] Table 1: Non-metallic inclusion content in Examples 1 and 2

[0085]

Claims

1. A method for preparing pure recycled high-temperature alloy raw materials using high-temperature alloy reclaimed materials, characterized in that, The process includes the following steps: (1) Ingredient preparation; (2) Loading; (3) Melting in an induction furnace; (4) Slag removal; (5) Take the components and prepare carbon; (6) AOD furnace smelting; (7) Take the components and pour them.

2. The method for preparing pure recycled high-temperature alloy raw materials using high-temperature alloy recycled materials according to claim 1, characterized in that, In step (1), The batching is based on the information of the inventory of high-temperature alloy recycled materials, including steel grades, specifications and shapes, combined with the main element composition requirements of the final required recycled high-temperature alloy raw material grade, to calculate the demand of high-temperature alloy recycled materials of different steel grades, specifications and shapes, and form a batching list for the medium-frequency furnace; the preparation of materials is the high-temperature alloy recycled materials and corresponding smelting auxiliary materials prepared according to the batching list of the medium-frequency furnace on site.

3. The method for preparing pure recycled high-temperature alloy raw materials using high-temperature alloy recycled materials according to claim 1, characterized in that, In step (2), During the loading process, based on the actual proportions, shapes, and specifications of the high-temperature alloy return material, first, small-sized block materials are loaded into the bottom of the medium-frequency furnace, then, shavings and wood chips are placed on top of the small blocks, and finally, large blocks of high-temperature alloy return material are placed on top of the crucible.

4. The method for preparing pure recycled high-temperature alloy raw materials using high-temperature alloy recycled materials according to claim 1, characterized in that, In step (3), After liquid steel appears in the crucible of the medium-frequency furnace, slag is formed and smelted by covering the surface of the high-temperature alloy steel with smelting auxiliary materials until the temperature in the furnace reaches ≥1700℃.

5. The method for preparing pure recycled high-temperature alloy raw materials using high-temperature alloy recycled materials according to claim 1, characterized in that, In step (4), The slag removal process involves pouring all the high-temperature alloy steel liquid from the medium-frequency furnace into the tundish, moving the tundish to the slag removal station, using a slag removal rake to remove all the floating slag from the upper layer of the molten steel in the tundish, and then pouring the high-temperature alloy steel liquid back into the medium-frequency furnace.

6. The method for preparing pure recycled high-temperature alloy raw materials using high-temperature alloy recycled materials according to claim 1, characterized in that, In step (5), The high-temperature alloy steel liquid returned to the intermediate frequency furnace after slag removal is subjected to composition analysis. Carbon addition is performed based on the C content in the steel liquid, and a carbon raiser is added to control the carbon content to the target value of 0.4-0.7%. The steel liquid is tapped when the temperature is controlled to be ≥1650℃, and the high-temperature alloy steel liquid is poured into the tundish.

7. The method for preparing pure recycled high-temperature alloy raw materials using high-temperature alloy recycled materials according to claim 1, characterized in that, In step (6), The AOD furnace smelting process involves pouring all the high-temperature alloy steel liquid from the tundish into the AOD furnace for argon-oxygen decarburization and refining purification.

8. The method for preparing pure recycled high-temperature alloy raw materials using high-temperature alloy recycled materials according to claim 7, characterized in that, During argon-oxygen decarburization, a mixture of argon and oxygen is blown into the molten steel through the top lance and bottom side vents according to the carbon content. This raises the temperature of the molten steel to above 1700℃. The volume ratio of argon to oxygen in the mixture is 1:6 to 1:

3. During the process, carbon samples are taken. When the carbon content reaches <0.05%, the decarburization operation ends, and the reduction stage begins. Al blocks and Si powder are used to reduce the precious metal elements, including Cr and Nb, in the molten steel and slag. At the same time, lime and CaF2 are added to form slag and remove sulfur. The steel composition and temperature are adjusted during the reduction process.

9. The method for preparing pure recycled high-temperature alloy raw materials using high-temperature alloy recycled materials according to claim 1, characterized in that, In step (7), After the reduction is completed in the AOD furnace smelting stage, a sample of the composition in the furnace is taken. If it meets the requirements of the main element and residual element composition of the recycled high-temperature alloy raw material, it is lifted out and poured. The lifting temperature is controlled at 1510~1580℃.

10. The method for preparing pure recycled high-temperature alloy raw materials using high-temperature alloy recycled materials according to claim 9, characterized in that, The residual element composition of the cast recycled high-temperature alloy raw materials shall meet the requirements of C < 0.05%, Si < 0.5%, Al < 1.0% and Ti < 0.8%. The coarse and fine non-metallic inclusions of Class A, Class C, and Class Ds shall be ≤ 0 grade, and the coarse and fine non-metallic inclusions of Class B and Class D shall be ≤ 0.5 grade.

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