A method of smelting a ferro-nickel based alloy

Abstract

The present application relates to the field of smelting, and particularly relates to a smelting method of iron-nickel-based alloy. The method comprises the following steps: electric furnace smelting, AOD furnace refining, LF furnace refining, VOD furnace refining, ingot casting, and due to process adjustment of each step, the molten steel can be directly cast into ingot after the VOD furnace refining step without electric slag remelting operation, so that the process steps are shortened and the production efficiency is improved. Due to the reduction of the electric slag remelting process flow, the smelting process of the present application can reduce the electric slag cost by 2000-3500 yuan / ton, can also avoid 3-5% metal loss caused by head and tail cutting and surface polishing treatment of the consumable electrode before electric slag remelting, and effectively avoids the uneven composition of the ingot head and tail caused by element burning loss in the electric slag remelting process.

Description

Technical Field

[0001] This invention relates to the field of metallurgy, and more particularly to a method for smelting an iron-nickel based alloy. Background Technology

[0002] A286 alloy is an iron-nickel-based wrought superalloy containing Ti, Al, and other trace alloying elements. Its precipitation hardening is primarily achieved through controlled aging precipitation of the γ' phase Ni3(Ti,Al) via post-deformation heat treatment. A286 alloy possesses excellent comprehensive mechanical properties and corrosion resistance, with an operating temperature range of −253℃ to 650℃. Due to its superior performance, A286 alloy has wide applications in aerospace, energy, and chemical industries. In the aerospace field, A286 alloy is commonly used to manufacture high-temperature load-bearing components for aero-engines that operate continuously below 650℃, such as turbine disks, compressor disks, rotor blades, and fasteners. These components not only need to operate at high temperatures but also frequently face various dynamic loads and vibrations; the excellent properties of A286 alloy ensure the safe and efficient operation of these components.

[0003] The current common smelting method for A286 alloy products is to use an electric furnace and refining process to produce electrode rods. After the electrode rods are flattened and polished, they are then subjected to electroslag remelting. This process is lengthy, has a low yield, and high manufacturing costs. Furthermore, since A286 alloy is an aluminum-titanium steel, the unavoidable loss of aluminum and titanium during electroslag remelting results in uneven composition at the beginning and end of the produced steel ingots. Summary of the Invention

[0004] This invention proposes a short-process smelting technology for A286 alloy, consisting of electric furnace, refining, and ingot casting. This reduces the electroslag remelting step, thereby improving production efficiency and lowering smelting costs. By rationally setting the process, the alloy microstructure and properties can be ensured to be comparable to those of the electroslag remelting process, and the process can also guarantee the uniformity of the steel ingot composition.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] A method for smelting an iron-nickel-based alloy includes the following steps: electric furnace smelting; AOD furnace refining; LF furnace refining; VOD furnace refining; and ingot casting. After the VOD furnace refining step, there is no need for electroslag remelting, and the molten steel obtained can be directly cast into ingots.

[0007] Preferably, the electric furnace smelting steps are as follows:

[0008] 1) If the furnace charge melting temperature is >1550℃, an appropriate amount of carbonized rice husks can be added to the furnace to prevent slag from crusting.

[0009] 2) Sampling and analysis of all elements to provide a reference for the initial adjustment of AOD composition;

[0010] 3) T at tapping temperature ≥ 1650℃, C ≥ 1.2%.

[0011] More preferably, in the electric furnace smelting step 1), the amount of carbonized rice husk added is 20-40 kg / 20 t of molten steel.

[0012] Preferably, in the AOD furnace refining step, the reduction period first adopts full Al reduction without adding Si; the secondary reduction adds 300-400 kg of reducing slag quicklime per 20 t of molten steel, 100-300 kg of fluorite per 20 t of molten steel, and 2-4 kg of Al ingots or Al granules per t of molten steel.

[0013] More preferably, the AOD furnace refining step is as follows:

[0014] 1) The AOD furnace temperature before steel pouring should be ≥800℃; the gas supply parameters should meet P 氧 ≥1.5MPa, P 氩 ≥1.5MPa;

[0015] 2) Ar = 500~700 Nm before steel mixing 3 / h, cooling air flow rate 130~350 Nm 3 / h;

[0016] 3) After the molten steel is poured into the AOD furnace, Ti and Si are blown out and samples are taken for analysis. If Ti ≤ 0.25% and Si ≤ 0.25%, slag is removed.

[0017] 4) During AOD decarbonization, the total gas flow rate is controlled at 1100~1500 Nm³. 3 / h;

[0018] 5) When C ≤ 0.3%, add Al for reduction, and use full Al reduction during the reduction period without adding Si;

[0019] 6) After reduction, shake the furnace to measure the temperature, take samples, and remove slag. ≥90% reduction is achieved. For secondary reduction, add 300-400 kg of quicklime / 20t of molten steel, 100-300 kg of fluorite / 20t of molten steel, and 2-4 kg of Al ingots or Al granules / t of molten steel. The reduction time is >5 minutes.

[0020] 7) The target for controlling the composition of the tapped steel is:

[0021] C: 0.150~0.30%; P: ≤0.035%; S: ≤0.003%; Si: ≤0.20%; Cr: 13.0~14.5%; Ni: 24.0~24.5%; Mo: 1.05~1.12%.

[0022] Preferably, the LF furnace refining process includes the following steps:

[0023] 1) After the molten steel arrives, adjust the argon flow rate to power the heating. During the heating process, add lime and fluorite according to the actual situation to adjust the fluidity of the slag.

[0024] 2) Add an appropriate amount of aluminum granules for diffusion deoxidation, adding small amounts frequently to maintain a reducing atmosphere inside the ladle; wait until the slag turns white for more than 10 minutes and the temperature is ≥1580℃, stir with strong argon gas for more than 3 minutes, and then take a full analysis sample. After the sample is returned, adjust the composition according to the following target values:

[0025] C: 0.150~0.30%; Mn: 1.0~1.1%; Ni: 24.5~25.0%; Cr: 14.0~14.5%; Mo: 1.05~1.12%; V: 0.20~0.30%;

[0026] 3) After the molten steel composition meets the requirements described in step 2), S≤0.002%, the ladle is used for slag removal, and the ladle temperature is ≥1650℃.

[0027] Preferably, the VOD furnace refining process includes the following steps:

[0028] 1) Remove slag before pouring into the ladle to ensure that ≥70% of the molten steel is exposed;

[0029] 2) After covering, perform vacuum oxygen blowing;

[0030] 3) After oxygen is shut off, the temperature is measured by breaking the air, and slag-forming materials and deoxidizers are added: lime 30~40 kg / t molten steel; calcium silicate blocks 1-3 kg / t molten steel; aluminum granules 6~8 kg / t molten steel;

[0031] 4) After adding the slag, open the tank cover truck, close the cover, and then vacuum degas the tank. Maintain a pressure of ≤67Pa for ≥15 minutes.

[0032] 5) After breaking the air, measure the temperature and return to the LF furnace for Al powder or calcium silicate reduction. If the white slag time is ≥20min, take a gas sample. If the target O is ≤20ppm and the temperature is ≥1630℃, remove the slag and scrape it off. Scrape the slag until the slag thickness is ≤100 mm, feed Al, and then add metallic titanium (according to the internal control standard). After adding metallic titanium, stir with argon gas for 5 minutes and take a full analysis sample.

[0033] 6) After the composition is qualified, use soft blowing, and insert ferroboron wrapped in aluminum foil 10 minutes before tapping;

[0034] 7) Tap the steel.

[0035] Further preferably, in step 5) of the VOD furnace refining process, Al is fed according to internal control standards, and in step 6), ferroboron wrapped in aluminum foil is added according to internal control standards. The internal control standards are: C: ≤0.03%; Mn: ≤1.30%; Si: ≤0.5%; S: ≤0.002%; P: ≤0.035%; Cr: 13.5~15.0%; Al: 0.13~0.28%; Ti: 2.00~2.30%; Ni: 24.3~25.0%; B: 0.004~0.007%; Mo: 1.05~1.15%; V: 0.20~0.30%; the balance is Fe.

[0036] More preferably, the soft blowing time of the VOD furnace refining step 6) is ≥20 min.

[0037] More preferably, in the VOD furnace refining step 7), the tapping temperature is 1520℃~1540℃.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The process of this invention reduces the electroslag remelting process, shortens the process steps, and improves production efficiency.

[0040] The process of this invention reduces the electroslag remelting process and reduces electroslag costs by 2,000-3,500 yuan / ton.

[0041] Before electroslag remelting, the consumable electrode needs to be trimmed at both ends and its surface polished, resulting in a loss of approximately 3-5% of metal utilization. The smelting process proposed in this solution can effectively avoid the above-mentioned metal loss.

[0042] The process proposed in this invention effectively avoids the uneven composition of the steel ingot head and tail caused by element burn-off during the electroslag remelting process. Detailed Implementation

[0043] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, the embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0044] The standard chemical composition of A286 alloy is as follows: C: ≤0.08%; Mn: ≤2.00%; Si: ≤1.0%; S: ≤0.03%; P: ≤0.04%; Cr: 13.50~16.00%; Al: ≤0.35%; Ti: 1.85~2.35%; Ni: 24.00~27.00%; B: 0.001~0.010%; Mo: 1.00~1.50%; Fe: balance; V: 0.10~0.50%.

[0045] The internal control standards for the chemical composition of the A286 alloy in the embodiments of this application are as follows: C: ≤0.03%; Mn: ≤1.30%; Si: ≤0.5%; S: ≤0.002%; P: ≤0.035%; Cr: 13.5~15.0%; Al: 0.13~0.28%; Ti: 2.00~2.30%; Ni: 24.3~25.0%; B: 0.004~0.007%; Mo: 1.05~1.15%; V: 0.20~0.30%; the balance is Fe.

[0046] Example 1

[0047] A method for smelting iron-nickel based alloys includes the following steps:

[0048] (1) Electric furnace smelting

[0049] 1) Full melting temperature of furnace charge: 1580℃. Add carbonized rice husks into the furnace at a rate of 25kg / 20t of molten steel to prevent slag from forming a crust.

[0050] 2) Tillage temperature: 1680℃, C: 1.4%.

[0051] (2) AOD furnace refining

[0052] 1) The AOD furnace temperature before steel pouring is 900℃. Gas supply parameters should meet P... 氧 1.6 MPa, P 氩 1.6 MPa.

[0053] 2) Ar = 600 Nm before steel addition 3 / h, cooling air flow rate 180 Nm 3 / h.

[0054] 3) After the molten steel was poured into the AOD furnace, Ti and Si were blown out and samples were taken for analysis. Ti: 0.1%; Si: 0.13%; slag removal treatment.

[0055] 4) During AOD decarbonization, the total gas flow rate is controlled at 1300 Nm³. 3 / h.

[0056] 5) C: 0.25%, add Al: 100kg for reduction.

[0057] 6) After reduction, remove 90% of the slag. For the second reduction, add 350 kg of lime, 200 kg of fluorite, and 80 kg of Al ingots. The reduction time is 8 minutes.

[0058] 7) AOD steel composition:

[0059] C: 0.20%; P: 0.03%; S: 0.002%; Si: 0.2%; Cr: 13.8%; Ni: 24.2%; Mo: 1.10%.

[0060] (3) LF furnace refining

[0061] 1) After the molten steel arrives, adjust the argon flow rate to power the heating and adjust the fluidity of the slag.

[0062] 2) Add an appropriate amount of 20 kg of aluminum granules for diffusion deoxidation, maintaining a reducing atmosphere inside the ladle. After the slag turns white for 12 minutes and the temperature reaches 1600℃, stir with a large amount of argon gas for 3 minutes and then take a complete analysis sample.

[0063] 3) Steel composition at LF tapping: C: 0.21%; Mn: 1.1%; Ni: 24.5%; Cr: 14.0%; Mo: 1.05%; V: 0.20%; S: 0.001%. Slag removal was performed using a ladle, with a ladle temperature of 1658℃.

[0064] (4) VOD furnace refining

[0065] 1) Remove slag before pouring into the ladle, exposing 80% of the molten steel area.

[0066] 2) After covering, perform vacuum oxygen blowing operation.

[0067] 3) After oxygen is stopped, the air is broken and the temperature is measured. Add slag-forming materials and deoxidizer: 600 kg of lime; 40 kg of calcium silicate blocks; and 120 kg of aluminum granules.

[0068] 4) After adding the slag, open the tank cover truck, close the cover, and then vacuum degas it at 65 Pa for 15 minutes.

[0069] 5) After breaking the air, measure the temperature, return to the LF furnace and add 12kg of Al powder for reduction. The white slag time is 20min. Take a gas sample. O: 20ppm, temperature 1635℃. Remove the slag and scrape it until the slag thickness is 80 mm. Feed Al into the furnace according to the internal control standard. After feeding Al, add metallic titanium.

[0070] 6) After the composition is qualified, blow softly for 24 minutes, and insert ferroboron wrapped in aluminum foil 10 minutes before tapping (add according to internal control standards).

[0071] 7) Tack temperature: 1530℃.

[0072] 8) The total furnace load is 20t, and 10 2t ingots are cast.

[0073] Example 2

[0074] A method for smelting iron-nickel based alloys includes the following steps:

[0075] (1) Electric furnace smelting

[0076] 1) Full melting temperature of furnace charge: 1585℃. Add 27kg of carbonized rice husks into the furnace to prevent slag from crusting.

[0077] 2) Tillage temperature: 1683℃, C: 1.5%.

[0078] (2) AOD furnace refining

[0079] 1) The AOD furnace temperature before steel pouring is 910℃. Gas supply parameters should meet P... 氧 1.6 MPa, P 氩 1.6 MPa.

[0080] 2) Ar = 600 Nm before steel addition 3 / h, cooling air flow rate 200 Nm 3 / h.

[0081] 3) After the molten steel was poured into the AOD furnace, Ti and Si were blown out and samples were taken for analysis. Ti: 0.12%; Si: 0.11%. Slag was removed.

[0082] 4) During AOD decarbonization, the total gas flow rate is controlled at 1300 Nm³. 3 / h.

[0083] 5) C: 0.24%, add Al: 100kg for reduction.

[0084] 6) After reduction, remove 90% of the slag. For the second reduction, add 350 kg of lime, 200 kg of fluorite, and 80 kg of Al ingots. The reduction time is 10 minutes.

[0085] 7) AOD steel composition: C: 0.21%; P: 0.03%; S: 0.002%; Si: 0.2%; Cr: 13.9%; Ni: 24.3%; Mo: 1.10%.

[0086] (3) LF furnace refining

[0087] 1) After the molten steel is in place, adjust the argon flow rate to power the heating and adjust the fluidity of the slag.

[0088] 2) Add 20 kg of aluminum granules for diffusion deoxidation, maintaining a reducing atmosphere inside the ladle. After the slag turns white for 12 minutes and the temperature reaches 1600℃, stir with a large amount of argon gas for 4 minutes and then take a complete analysis sample.

[0089] 3) Steel composition at LF tapping: C: 0.21%; Mn: 1.1%; Ni: 24.5%; Cr: 14.0%; Mo: 1.10%; V: 0.20%; S: 0.001%. Slag removal was performed using a ladle, with a ladle temperature of 1658℃.

[0090] (4) VOD furnace refining

[0091] 1) Remove slag before pouring into the ladle, exposing 80% of the molten steel area.

[0092] 2) After covering, perform vacuum oxygen blowing operation.

[0093] 3) After oxygen is stopped, the air is broken and the temperature is measured. Add slag-forming materials and deoxidizer: 600 kg of lime; 40 kg of calcium silicate blocks; and 120 kg of aluminum granules.

[0094] 4) After adding the slag, open the tank cover truck, close the cover, and then vacuum degas the tank, maintaining 65Pa for 18 minutes.

[0095] 5) After breaking the air, measure the temperature, return 15kg of Al powder to the LF furnace for reduction, white slag time is 21min, take a gas sample, O: 18ppm, temperature 1638℃, remove the slag and scrape the slag until the slag thickness is 80 mm, feed Al into the furnace according to the internal control standard, and add metallic titanium after feeding Al.

[0096] 6) After the composition is qualified, blow softly for 25 minutes, and insert ferroboron wrapped in aluminum foil 10 minutes before tapping (add according to internal control standards).

[0097] 7) Tack temperature: 1535℃.

[0098] 8) The total furnace load is 20t, and 10 2t ingots are cast.

[0099] The comparative process route is electric furnace + AOD + LF + VOD + electroslag remelting, where the steps of electric furnace + AOD + LF + VOD are the same as in Example 1, and will not be repeated below. The main process parameters for electroslag remelting (based on a 2t electroslag ingot) are as follows.

[0100] 1) Slag system: CaF2:Al2O3:CaO = 75%:15%:10%.

[0101] 2) Slag volume 72-80kg.

[0102] 3) Electrical parameters: Voltage: 60~66V, Current: 8300~9300A.

[0103] 4) The following shows the electroslag remelting parameters for comparison.

[0104] Comparative Example 1: The slag system was CaF2:Al2O3:CaO = 75%:15%:10%, the slag amount was 72kg, the voltage was 65V, and the current was 8400A.

[0105] Comparative Example 2: The slag system was CaF2:Al2O3:CaO = 75%:15%:10%, the slag amount was 76kg, the voltage was 64V, and the current was 8800A;

[0106] All details not described above, except for process parameters, are standard operating procedures in this industry and will not be elaborated further.

[0107] The following are comparative results of the cases: 1. Comparison of inclusion levels (Table 1); 2. Comparison of easily burnable components (Table 2); 3. Ingot yield and cost. The example is produced using the process of this invention, while the comparative example is produced using the traditional electroslag remelting smelting method.

[0108] Table 1. Comparison of Inclusion Levels

[0109]

[0110] Table 1 shows that the inclusions in the steel ingots produced by this invention are comparable to those produced through the electroslag remelting process.

[0111] Table 2. Comparison of Easily Burnable Components

[0112]

[0113] Table 2 shows that the composition of the steel ingot produced by the present invention avoids the uneven composition of the ingot head and tail caused by the different burning patterns of easily burned elements at the head and tail of the ingot during the electroslag remelting process.

[0114] Ingot yield and cost

[0115] The smelting method in Comparative Example 1 first produces consumable electrode rods, which are then processed through electroslag remelting. Before electroslag remelting, the consumable electrodes need to be trimmed and polished, resulting in a loss of approximately 3-5% in metal utilization. Furthermore, the cost per ton of steel after electroslag remelting is between 2000-3500 yuan. The smelting process proposed in this scheme can effectively avoid the above-mentioned metal loss and smelting costs, while also reducing the number of steps and improving production efficiency.

Claims

1. A method for smelting an iron-nickel-based alloy, characterized in that, Includes the following steps: Electric furnace smelting; AOD furnace refining; LF furnace refining; VOD furnace refining; ingot casting; after the VOD furnace refining step, there is no need for electroslag remelting, and the molten steel obtained can be directly cast into ingots; The electric furnace smelting steps are as follows: 1) If the furnace charge has a full melting temperature > 1550℃, carbonized rice husks are added to the furnace to prevent slag crusting. 2) Sampling and analysis of all elements to provide a reference for the initial adjustment of AOD composition; 3) Tating temperature ≥ 1650℃, C ≥ 1.2%; In the electric furnace smelting step 1), the amount of carbonized rice husk added is 20-40 kg / 20 t of molten steel; The AOD furnace refining steps are as follows: 1) The AOD furnace temperature before steel pouring should be ≥800℃; the gas supply parameters should meet P 氧 ≥1.5MPa, P 氩 ≥1.5MPa; 2) The Ar flow rate before steel mixing is 500~700 Nm 3 / h, cooling air flow rate is 130~350 Nm 3 / h; 3) After the molten steel is poured into the AOD furnace, Ti and Si are blown out and samples are taken for analysis. If Ti ≤ 0.25% and Si ≤ 0.25%, slag is removed. 4) During AOD decarbonization, the total gas flow rate is controlled at 1100~1500 Nm³. 3 / h; 5) When C ≤ 0.3%, add Al for reduction, and use full Al reduction during the reduction period without adding Si; 6) After reduction, shake the furnace to measure the temperature, take samples, and remove slag. ≥90% reduction is achieved. For secondary reduction, add 300-400 kg of quicklime / 20t of molten steel, 100-300 kg of fluorite / 20t of molten steel, and 2-4 kg of Al ingots or Al granules / t of molten steel. The reduction time is >5 minutes. 7) The target for controlling the composition of the tapped steel is: C: 0.150~0.30%; P: ≤0.035%; S: ≤0.003%; Si: ≤0.20%; Cr: 13.0~14.5%; Ni: 24.0~24.5%; Mo: 1.05~1.12%; The LF furnace refining process includes the following steps: 1) After the molten steel arrives, adjust the argon flow rate to power the heating. During the heating process, add lime and fluorite according to the actual situation to adjust the fluidity of the slag. 2) Add an appropriate amount of aluminum granules for diffusion deoxidation, adding small amounts frequently to maintain a reducing atmosphere inside the ladle; wait until the slag turns white for more than 10 minutes and the temperature is ≥1580℃, stir with strong argon gas for more than 3 minutes, and then take a full analysis sample. After the sample is returned, adjust the composition according to the following target values: C: 0.150~0.30%; Mn: 1.0~1.1%; Ni: 24.5~25.0%; Cr: 14.0~14.5%; Mo: 1.05~1.12%; V: 0.20~0.30%; 3) After the molten steel composition meets the requirements described in step 2), S≤0.002%, the ladle is used for slag removal, and the ladle temperature is ≥1650℃; The VOD furnace refining process includes the following steps: 1) Remove slag before pouring into the ladle to ensure that ≥70% of the molten steel is exposed; 2) After covering, perform vacuum oxygen blowing; 3) After oxygen is shut off, the temperature is measured by breaking the air, and slag-forming materials and deoxidizers are added: lime 30~40 kg / t molten steel; calcium silicate blocks 1-3 kg / t molten steel; aluminum granules 6~8 kg / t molten steel; 4) After adding the slag, open the tank cover truck, close the cover, and then vacuum degas the tank. Maintain a pressure of ≤67Pa for ≥15 minutes. 5) After breaking the air, measure the temperature and return to the LF furnace for Al powder or silicon-calcium powder reduction. If the white slag time is ≥20min, take a gas sample. If the target O is ≤20ppm and the temperature is ≥1630℃, remove the slag and scrape it off. Scrape the slag until the slag thickness is ≤100 mm, feed Al, and then add metallic titanium according to the internal control standard. After adding metallic titanium, stir with argon gas for 5 minutes and take a full analysis sample. 6) After the composition is qualified, use soft blowing, and insert ferroboron wrapped in aluminum foil 10 minutes before tapping; 7) Tapping steel; In step 5) of the VOD furnace refining process, Al is fed according to internal control standards. In step 6), ferroboron wrapped in aluminum foil is added according to internal control standards, which are: C: ≤0.03%; Mn: ≤1.30%; Si: ≤0.5%; S: ≤0.002%; P: ≤0.035%; Cr: 13.5~15.0%; Al: 0.13~0.28%; Ti: 2.00~2.30%; Ni: 24.3~25.0%; B: 0.004~0.007%; Mo: 1.05~1.15%; V: 0.20~0.30%; the balance is Fe. The soft blowing time of the VOD furnace refining step 6) is ≥20 min; In the VOD furnace refining step 7), the tapping temperature is 1520℃~1540℃.

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