Vacuum induction furnace smelting process of Nb-containing high-temperature alloy

Abstract

The application discloses a vacuum induction furnace smelting process of Nb-containing high-temperature alloy and belongs to the technical field of vacuum induction furnace metallurgy. The process is characterized in that metal Nb is added in the melting period, and the smelting process conditions are controlled, so that the smelted induction ingot is stable in alloy element composition, the Nb element uniformity in the GH4169 electrode rod is improved, the Nb segregation is reduced, the C-O reaction is more intense in the melting period, the [O] content in the electrode rod is reduced, the [O] and [N] gases are sufficiently removed in the melting period, the refining period length can be controlled to be within 1.5 hours, the smelting length in the refining period is reduced by 1-2 hours, the reduction corrosion of the high-temperature refined alloy liquid to the crucible in the refining period is slowed down, the cost is reduced, and the purpose of sustainable green development is met.

Description

Technical Field

[0001] This invention belongs to the field of vacuum induction furnace metallurgical technology, specifically relating to a vacuum induction furnace smelting process for Nb-containing high-temperature alloys. Background Technology

[0002] GH4169 alloy is currently the most widely used precipitation-strengthened nickel-based superalloy, mainly used in aero-engine turbine disks, guide vanes, and hot-end components of ground gas turbines. Due to its chemical composition and the solidification conditions of the alloy ingot, GH4169 alloy is prone to severe compositional segregation. Nitrogen (Nb), as the most important alloying element for γ″ strengthening, plays a crucial role in alloy strengthening but is also the most significant segregating element. Nb segregation leads to the formation of Nb-rich blocky Laves phases, drastically reducing the alloy's impact resistance and plasticity. Simultaneously, Nb and Ti enrichment between dendrites and Nb and Ti depletion in dendritic stems result in coarse-fine grain banding in the finished product, causing inhomogeneity in microstructure and properties that directly impacts product quality. In the current process of smelting GH4169, Nb is added in the later stages of refining, which is detrimental to controlling Nb segregation. Furthermore, adding Nb in the later stages of refining hinders the removal of [O] from metallic Nb, leading to the formation of numerous oxide inclusions in the alloy melt. These problems severely affect the final product quality and restrict the manufacturing and development of high-quality high-temperature alloys. To improve the quality of high-temperature alloy vacuum induction smelting products, research on optimization methods for high-temperature alloy vacuum induction smelting processes is urgently needed. Summary of the Invention

[0003] Therefore, the purpose of this invention is to provide a vacuum induction furnace smelting process for Nb-containing high-temperature alloys. The process of this invention adds metallic Nb during the melting period and, combined with controlled smelting conditions, improves the uniformity of Nb in the GH4169 electrode rod, reducing Nb segregation; the CO reaction is more intense during the melting period, reducing the [O] content in the electrode rod; and [O] and [N] gases are sufficiently removed during the melting period, allowing the refining period to be controlled to within 1.5 hours, reducing the refining time by 1-2 hours, mitigating the reduction erosion of the crucible by the high-temperature refined alloy liquid during the refining period, and simultaneously reducing costs, aligning with the current goals of sustainable green development.

[0004] The objective of this invention is achieved through the following means:

[0005] This invention provides a vacuum induction furnace smelting process for Nb-containing high-temperature alloys. The chemical element composition and weight percentage of the Nb-containing high-temperature alloy are as follows: Ni: 51.0-55.0%, Cr: 17.0-20.0%, Nb: 5.0-5.5%, Mo: 2.90-3.20%, Al: 0.45-0.65%, Ti: 0.95-1.15%, Fe: 17.0-19.0%, C: 0.02-0.04%, S≤0.003%, N≤0.005%, O≤0.002%, with the balance being unavoidable impurities.

[0006] The main steps include:

[0007] (1) Batching: Within 24 hours before smelting, the metal raw materials Fe, Nb and Mo are tumbled or shot blasted to remove rust and oil stains. Only when the surface has a metallic luster can they be put into the furnace for smelting.

[0008] (2) Melting: Electrolytic nickel, metallic Cr, metallic Fe, and metallic Mo are added to the crucible in sequence. 30-70% of the total amount of C blocks are added. The furnace is closed and a vacuum is drawn. When the vacuum level is below 5 Pa, power is supplied. After the material is leveled, the temperature is controlled at 1480-1520℃. All metallic Nb and 40-60% of the remaining C blocks are added through the side feeding device. The temperature is maintained at 1480-1520℃, and the mixture is stirred at industrial frequency for 1-5 hours to remove gas.

[0009] (3) Refining: Heat to 1520~1560℃ for refining, stir at industrial frequency to ensure degassing and uniformity of composition, vacuum degree ≤0.8Pa. Since metal Nb has been added during the melting period, the refining time is shortened to 1~1.5h.

[0010] (4) Alloying: After refining, power is cut off to allow the alloy to form a film under high vacuum. The remaining C block is added, along with Al and Ti. Power is supplied to melt the alloy, and the temperature is controlled at 1500-1550℃. The mixture is stirred at industrial frequency for 0.5-1h to ensure sufficient deoxidation and nitrogen removal, and that the deoxidation and nitrogen removal products float to the surface of the alloy liquid or are adsorbed and removed by the crucible wall. Ar is charged at 3000-10000Pa, and then 0.05-0.5% Ni-Mg is added for alloying. The mixture is stirred at industrial frequency and maintained for 3-10min.

[0011] (5) Casting and solidification: The steel is tapped at 1400-1500℃, vacuum cast, and the casting is removed after natural cooling.

[0012] Based on the above technical solution, the chemical element composition and weight percentage of the Nb-containing high-temperature alloy are further as follows: Ni: 52.0-54.0%, Cr: 18.0-19.0%, Nb: 5.0-5.5%, Mo: 2.90-3.20%, Al: 0.45-0.65%, Ti: 0.95-1.15%, Fe: 17.0-19.0%, C: 0.02-0.04%, S≤0.003%, N≤0.005%, O≤0.002%, with the balance being unavoidable impurities.

[0013] Based on the above technical solution, further, the Ni, Cr, Fe, Mo, Nb, Al and Ti mentioned in step (1) are selected from pure metal raw materials.

[0014] Based on the above technical solution, further, in step (1), the total amount of harmful elements introduced from the raw materials [O] ≤ 250 ppm and [N] ≤ 70 ppm.

[0015] Based on the above technical solution, further, in step (2), the melting temperature is controlled at 1490~1510℃; 40~60% of the total amount of C blocks are added; power is supplied when the vacuum degree is lower than 1Pa; and the gas is removed by stirring at industrial frequency for 3~4 hours.

[0016] Since Nb is a solid nitrogen element, it is usually added after deep nitrogen removal during the refining stage (under high-temperature refining conditions). This results in a late addition of Nb, leading to a high [O] content in the raw Nb. Furthermore, the addition of Al and Ti alloying in the later stages of smelting easily generates a large number of oxide inclusions that cannot be fully removed. Additionally, adding metallic Nb after the refining stage, with a later smelting time, is not conducive to the uniform distribution of Nb in the alloy liquid, causing severe Nb segregation in the induction ingot. Adding metallic Nb during the melting stage, along with 3–4 hours of industrial frequency stirring, extends the smelting time of Nb in the alloy liquid, improving its uniformity and reducing Nb segregation. Moreover, the high [O] content in metallic Nb leads to greater carbon loss, making the CO reaction more significant during the melting stage. The more vigorous the CO reaction, the higher the content of [N] removed. This ensures more thorough removal of [O] and [N] during the melting stage, avoiding the large-scale formation of oxide and nitride inclusions in the later stages of smelting.

[0017] Based on the above technical solution, further, the refining temperature in step (3) is controlled at 1530~1540℃.

[0018] Based on the above technical solution, in step (4), the alloying temperature is controlled at 1510~1540℃; Ar is charged at 4000~6000Pa.

[0019] Based on the above technical solution, further, in step (5), the tapping temperature is controlled at 1440~1460℃.

[0020] The advantages of this invention over the prior art are as follows:

[0021] This invention develops a vacuum induction furnace smelting process for Nb-containing high-temperature alloys. Metallic Nb is added during the melting period, and combined with controlled smelting process conditions, the alloy element composition of the smelted induction ingot is stable, improving the uniformity of Nb in the GH4169 electrode rod and reducing Nb segregation. The more intense CO reaction during melting reduces the [O] content in the electrode rod. Sufficient removal of [O] and [N] gases during melting allows the refining period to be controlled within 1.5 hours, reducing the refining time by 1-2 hours, mitigating the reduction erosion of the crucible by the high-temperature refined alloy liquid, and simultaneously lowering costs, aligning with current goals of sustainable green development. Detailed Implementation

[0022] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0023] Comparative Example 1

[0024] This comparative example provides a process for smelting GH4169 alloy in a vacuum induction furnace, the specific process of which is as follows:

[0025] Ingredients: The main alloying elements Ni, Cr, Fe, Mo, Nb, Al, Ti, etc. are all pure metal materials. The total amount of harmful elements introduced is 237.5 ppm [O] and 62.5 ppm [N]. 24 hours before smelting, the raw materials Fe, Nb, Mo and other metal materials are tumbled to remove rust and oil stains until the surface has a metallic luster. They are then stored in a dry space for later use to avoid the raw materials from absorbing moisture and oxidizing again.

[0026] Melting period: After cleaning the crucible, load the materials, and add Ni, Cr, Fe and Mo raw materials into the crucible in a smooth manner. Add 1 / 3 of the total amount of C blocks for the first time, close the furnace and evacuate the vacuum. When the vacuum level drops to 0.9 Pa, start powering on. First, power on at a low power until the furnace charge metal turns completely red. When molten steel begins to appear at the bottom of the crucible, increase the power. After the material is level, add 1 / 3 of the total amount of C blocks for the second time, and stir at industrial frequency for 3.5 hours to remove gas.

[0027] Refining period: After the melting period, the temperature is raised to the refining temperature for refining, and the mixture is stirred at industrial frequency to ensure degassing and uniform composition. The refining temperature is controlled at 1558℃ and the vacuum degree is 0.4Pa, mainly for deep removal of nitrogen. After refining for 1 hour, metallic Nb is added for alloying, and then refined for another 1.5 hours for deep removal of oxygen and nitrogen. The total refining period lasts for 2.5 hours.

[0028] Alloying: After the refining period, the power is turned off, and the alloy forms a film under high vacuum. Then, 1 / 3 of the total amount of C block is added for the third time. Trace alloying elements Al and Ti are added for precipitation and deoxidation. The power supply temperature is 1525℃, and the mixture is stirred at the power frequency for 0.5h. Ar is charged at 5000Pa, and then 0.1% Ni-Mg is added for alloying. The mixture is stirred at the power frequency for 5min.

[0029] Casting and solidification: After alloying, the temperature is lowered to 1450℃ for tapping, and the steel is cast under vacuum to a diameter of [diameter missing]. Cast the ingot, allow it to cool naturally for 1 hour, and then remove the casting.

[0030] The Nb element segregation measurement and full elemental analysis were performed on the high-temperature alloy ingots produced by this process, and the results are shown in Table 1-2.

[0031] Example 1

[0032] This embodiment provides a new process for smelting GH4169 alloy in a vacuum induction furnace, the specific process of which is as follows:

[0033] Ingredients: The same batch of raw materials as Comparative Example 1 were used for smelting. The total amount of harmful elements introduced was 237.5 ppm [O] and 62.5 ppm [N]. 24 hours before smelting, the raw materials Fe, Nb, Mo and other metal materials were tumbled to remove rust and oil until the surface had a metallic luster. They were then stored in a dry space for later use to prevent the raw materials from absorbing moisture and oxidizing again.

[0034] Melting period: After cleaning the crucible, load the materials, and add Ni, Cr, Fe, and Mo raw materials into the crucible in a smooth manner. Add half of the total amount of C blocks for the first time, close the furnace and evacuate the vacuum. When the vacuum level drops to 1 Pa, start powering on. First, power on the furnace charge at a low power until the metal turns completely red. When molten steel begins to appear at the bottom of the crucible, increase the power. After the charge is leveled, control the temperature at 1500℃, and add all the metal Nb through side feeding. Add 1 / 4 of the total amount of C blocks for the second time. Maintain the temperature at 1500±10℃ and stir at industrial frequency for 4 hours to remove gas.

[0035] Refining period: After the melting period, the temperature is raised to the refining temperature for refining, and the mixture is stirred at industrial frequency to ensure degassing and uniform composition. The refining temperature is controlled at 1535℃ and the vacuum degree is 0.5Pa. Since the metal Nb has been added during the melting period, the refining time is shortened to 1.5h.

[0036] Alloying: After the refining period, the power is turned off, and the alloy forms a film under high vacuum. Then, 1 / 4 of the total amount of C block is added for the third time. Trace alloying elements Al and Ti are added for precipitation and deoxidation. The power supply temperature is 1530℃, and the mixture is stirred at the power frequency for 0.5h. Ar is charged at 5000Pa, and then 0.1% Ni-Mg is added for alloying. The mixture is stirred at the power frequency for 5min.

[0037] Casting and solidification: After alloying, the temperature is lowered to 1450℃ for tapping, and the steel is cast under vacuum to a diameter of [diameter missing]. Cast the ingot, allow it to cool naturally for 1 hour, and then remove the casting.

[0038] The Nb element segregation measurement and full elemental analysis were performed on the high-temperature alloy ingots produced by this process, and the results are shown in Table 1-2.

[0039] Example 2

[0040] This embodiment provides a new process for smelting GH4169 alloy in a vacuum induction furnace, the specific process of which is as follows:

[0041] Ingredients: The same batch of raw materials as Comparative Example 1 were used for smelting. The total amount of harmful elements introduced was 237.5 ppm [O] and 62.5 ppm [N]. 24 hours before smelting, the raw materials Fe, Nb, Mo and other metal materials were tumbled to remove rust and oil until the surface had a metallic luster. They were then stored in a dry space for later use to prevent the raw materials from absorbing moisture and oxidizing again.

[0042] Melting period: After cleaning the crucible, load the materials, and add Ni, Cr, Fe, and Mo raw materials into the crucible in a smooth manner. Add half of the total amount of C blocks for the first time, close the furnace and evacuate the vacuum. When the vacuum level drops to 0.9 Pa, start powering on. First, power on the furnace charge at a low power until the metal turns completely red. When molten steel begins to appear at the bottom of the crucible, increase the power. After the material is leveled, control the temperature at 1500℃, and add all the metal Nb through side feeding. Add 1 / 4 of the total amount of C blocks for the second time. Maintain the temperature at 1500±10℃ and stir at industrial frequency for 3 hours to remove gas.

[0043] Refining period: After the melting period, the temperature is raised to the refining temperature for refining, and the mixture is stirred at industrial frequency to ensure degassing and uniform composition. The refining temperature is controlled at 1538℃ and the vacuum degree is 0.5Pa. Since the metal Nb has been added during the melting period, the refining time is shortened to 1.5h.

[0044] Alloying: After the refining period, the power is turned off, and the alloy forms a film under high vacuum. Then, 1 / 4 of the total amount of C block is added for the third time. Trace alloying elements Al and Ti are added for precipitation and deoxidation. The power supply temperature is 1520℃, and the mixture is stirred at the power frequency for 0.5h. Ar is charged at 5000Pa, and then 0.1% Ni-Mg is added for alloying. The mixture is stirred at the power frequency for 5min.

[0045] Casting and solidification: After alloying, the temperature is lowered to 1445℃ for tapping, and the steel is cast under vacuum to a diameter of [diameter missing]. Cast the ingot, allow it to cool naturally for 1 hour, and then remove the casting.

[0046] The Nb element segregation measurement and full elemental analysis were performed on the high-temperature alloy ingots produced by this process, and the results are shown in Table 1-2.

[0047] Table 1 shows the segregation coefficient K of Nb, the main segregating element, in different parts of the induction ingots prepared in Comparative Example 1 and Examples 1-2.

[0048]

[0049] Table 2. Main chemical composition (wt%) of the alloy induction ingots prepared in Comparative Example 1 and Examples 1-2

[0050]

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A vacuum induction furnace smelting process for Nb-containing high-temperature alloys, characterized in that, The chemical element composition and weight percentage of the Nb-containing high-temperature alloy are as follows: Ni: 51.0~55.0%, Cr: 17.0~20.0%, Nb: 5.0~5.5%, Mo: 2.90~3.20%, Al: 0.45~0.65%, Ti: 0.95~1.15%, Fe: 17.0~19.0%, C: 0.02~0.04%, S≤0.003%, N≤0.005%, O≤0.002%, with the balance being unavoidable impurities; The main steps include: (1) Batching: Within 24 hours before smelting, the metal raw materials Fe, Nb and Mo are tumbled or shot blasted to remove rust and oil stains. Only when the surface has a metallic luster can they be put into the furnace for smelting. (2) Melting: Electrolytic nickel, metallic Cr, metallic Fe, and metallic Mo are added to the crucible in sequence. 40-60% of the total amount of C blocks are added. The furnace is closed and a vacuum is drawn. When the vacuum level is below 5 Pa, power is supplied. After the material is leveled, the temperature is controlled at 1490-1510℃. All metallic Nb and 40-60% of the remaining C blocks are added through the side feeding device. The temperature is maintained at 1480-1520℃ and the mixture is stirred at industrial frequency for 1-5 hours to remove gas. (3) Refining: Heat to 1530~1540℃ for refining, stir at industrial frequency to ensure degassing and uniformity of composition, vacuum degree ≤0.8Pa, refining time is 1~1.5h; (4) Alloying: After refining, the power is turned off, and the alloy forms a film under high vacuum. The remaining amount of C block is added, along with Al and Ti. The power is turned on to melt the alloy. The temperature is controlled at 1510~1540℃. The mixture is stirred at industrial frequency for 0.5~1h. Ar is charged at 3000~10000Pa. Then, 0.05~0.5% Ni-Mg is added for alloying. The mixture is stirred at industrial frequency and kept for 3~10min. (5) Casting and solidification: The steel is tapped at 1400~1500℃, vacuum cast, and the casting is removed after natural cooling.

2. The process according to claim 1, characterized in that, The chemical element composition and weight percentage of the Nb-containing high-temperature alloy are as follows: Ni: 52.0~54.0%, Cr: 18.0~19.0%, Nb: 5.0~5.5%, Mo: 2.90~3.20%, Al: 0.45~0.65%, Ti: 0.95~1.15%, Fe: 17.0~19.0%, C: 0.02~0.04%, S≤0.003%, N≤0.005%, O≤0.002%, with the balance being unavoidable impurities.

3. The process according to claim 1, characterized in that, The Ni, Cr, Fe, Mo, Nb, Al and Ti mentioned in step (1) are pure metal raw materials.

4. The process according to claim 1, characterized in that, In step (1), the total amount of harmful elements introduced from the raw materials is [O]≤250ppm and [N]≤70ppm.

5. The process according to claim 1, characterized in that, In step (2), power is supplied when the vacuum level is below 1 Pa; the gas is removed by stirring at industrial frequency for 3-4 hours.

6. The process according to claim 1, characterized in that, In step (4), Ar is charged at 4000~6000 Pa.

7. The process according to claim 1, characterized in that, In step (5), the tapping temperature is controlled at 1440~1460℃.

Images