Purified smelting method for nickel-based superalloy

Abstract

The invention discloses a pure smelting method for nickel-based superalloy, which relates to the technical field of metal smelting and comprises the following steps: (1) screening high-purity raw materials; (2) selecting a vacuum induction melting furnace and carrying out vacuumizing treatment; (3) sequentially adding the pretreated raw materials into a vacuum induction melting furnace, and heating and melting the raw materials; (4) carrying out electromagnetic stirring; (5) preparing special electroslag, and drying and crushing the electroslag; and (6) casting the alloy liquid subjected to vacuum melting into a consumable electrode, inserting the consumable electrode into the slag of the electroslag remelting furnace, and electrifying. According to the design scheme, impurities in the nickel-based superalloy are effectively removed, the purity and uniformity of the alloy are improved, the mechanical property and thermal stability of the alloy are improved, the service life is prolonged, and a better purification effect is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of metal smelting, in particular to a purification smelting method for nickel-based high-temperature alloys. Background Art

[0002] Nickel-based high-temperature alloys are widely used in key fields such as aerospace, energy, and chemical industry due to their excellent mechanical properties, oxidation resistance, and corrosion resistance at high temperatures. However, impurities in the alloy, such as gas impurities (oxygen, nitrogen, hydrogen, etc.), non-metallic inclusions (oxides, sulfides, etc.), and low-melting-point metal impurities, will seriously affect the performance and service life of the alloy. Traditional smelting methods have certain limitations in removing impurities and are difficult to meet the increasing application needs. Therefore, the development of an efficient purification smelting method is of great practical significance. Summary of the invention

[0003] In order to overcome the above-mentioned defects in the prior art, the present invention provides a purification smelting method for nickel-based high-temperature alloys.

[0004] The technical solution adopted by the present invention to solve the technical problem is: a purification smelting method for nickel-based high-temperature alloy, comprising the following steps:

[0005] ① Raw material screening: select high-purity raw materials of main alloy elements such as nickel, chromium, molybdenum, cobalt, etc., requiring the purity of each element to reach a certain level of more than 99.9%, and pre-treat its surface;

[0006] ② Select a vacuum induction melting furnace and perform vacuum treatment to reduce the pressure in the furnace to below 10^(-3)Pa;

[0007] ③ Add the pretreated raw materials into the vacuum induction melting furnace in order, heat and melt the raw materials, and strictly control the heating rate and melting temperature;

[0008] ④ Perform electromagnetic stirring, the frequency of electromagnetic stirring is controlled at 10Hz to 50Hz, and the stirring intensity is controlled at a magnetic field strength range of 0.05T to 0.2T, so that the alloy liquid is fully mixed, the alloy composition is homogenized, and the floating and discharge of gas and inclusions are promoted. The stirring time is 30 minutes to 1 hour;

[0009] ⑤ Prepare special electroslag, dry and crush the prepared electroslag raw materials, control the drying temperature at 200℃ to 300℃, and continue for 6 to 8 hours. After drying, crush the electroslag raw materials to a particle size of 0.5 mm to 2 mm;

[0010] ⑥ Cast the alloy liquid after vacuum melting into a consumable electrode, insert it into the slag of the electroslag remelting furnace and pass an electric current. Under the action of the electric current, the consumable electrode gradually melts, and the molten metal droplets pass through the slag layer and solidify into an ingot in the bottom crystallizer. The remelting rate is 5 to 10 kg per hour, and the cooling rate is 5°C to 10°C per minute to improve the solidification structure of the alloy and reduce the formation of segregation and inclusions.

[0011] Furthermore, in the step ①, the raw material is surface treated by a combination of mechanical grinding and chemical cleaning. After mechanical grinding to remove the oxide scale and rust on the surface, the raw material is soaked for 30 minutes to 1 hour. The cleaned raw material is rinsed with deionized water for multiple times until the resistivity of the rinse water reaches 18.2 MΩ·cm or more to ensure that the cleaning liquid and impurities on the surface are completely removed.

[0012] Furthermore, the washed raw material is dried at 80° C. to 120° C. until the surface of the raw material is dry and no moisture remains.

[0013] Furthermore, in step ③, the amount of nickel added is 50% to 60% of the total weight, and the amount of chromium added is 20% to 30%.

[0014] Furthermore, the heating rate in step ③ is generally controlled at 5°C to 10°C per minute to avoid local overheating of the raw materials or thermal stress due to too fast heating, and the smelting temperature is between 1400°C and 1600°C.

[0015] Furthermore, the content of calcium oxide in the electroslag prepared in step ⑤ is controlled to be 40% to 60%, and the content of aluminum oxide is 10% to 30%.

[0016] Furthermore, in step ⑥, the diameter of the consumable electrode is 50 mm to 100 mm, the length is 500 mm to 1000 mm, and the current passing through the consumable electrode is 1000A to 5000A.

[0017] Furthermore, in step ⑥, argon gas is introduced into the smelting equipment and the casting mold through a gas supply pipe and a nozzle, so that the argon gas is isolated from the air and prevents the alloy from reacting when in contact with the air at high temperature.

[0018] The beneficial effects of the present invention are:

[0019] 1. Effectively remove gas impurities and non-metallic inclusions in nickel-based high-temperature alloys, effectively remove low-melting-point metal impurities and other trace impurities, and improve the purity and uniformity of the alloy.

[0020] 2. High temperature strength is significantly improved, the tensile strength and yield strength of the alloy are improved, it can withstand greater loads, improve application reliability, and improve oxidation resistance and corrosion resistance. The oxidation rate of the alloy in a high temperature oxidation environment is significantly reduced, the corrosion resistance is enhanced, the microstructure of the alloy is more uniform, the mechanical properties and thermal stability of the alloy are improved, and the service life is extended.

[0021] 3. The process has high stability and reliability, the quality of the alloy is stable, and it is suitable for various types of nickel-based high-temperature alloys to achieve better purification effects. DETAILED DESCRIPTION

[0022] In order to more clearly illustrate the technical solution of the present invention, the present invention is further described below. Obviously, what is described below is only one embodiment of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on this embodiment without paying creative work, and they all belong to the protection scope of the present invention.

[0023] A purification smelting method for nickel-based high-temperature alloys comprises the following steps:

[0024] ① Selection and pretreatment of raw materials:

[0025] High-purity raw materials such as nickel, chromium, molybdenum and cobalt are selected, and the purity of each raw material is respectively: nickel 99.995%, chromium 99.96%, molybdenum 99.92%, and cobalt 99.91%.

[0026] The raw materials were surface treated by first grinding the raw material surface with a grinding wheel to remove the oxide scale and rust on the surface, then immersing the raw materials in a cleaning solution containing hydrochloric acid and hydrogen peroxide for 30 minutes, and then rinsing the cleaned raw materials with deionized water for 4 times until the resistivity of the rinse water reached 18.2 MΩ·cm to ensure that the cleaning solution and impurities on the surface were completely removed, and finally drying the raw materials in an oven at 90°C for 1.5 hours to ensure that the surface of the raw materials was dry without any moisture residue.

[0027] ②Vacuum melting stage:

[0028] The pretreated raw materials are added into a vacuum induction melting furnace and proportioned according to the ratio of 58% nickel, 22% chromium, 10% molybdenum and 10% cobalt.

[0029] The smelting furnace was vacuumed. First, the pressure inside the furnace was pumped down to 5Pa using a mechanical pump, and then the molecular pump was started to reduce the pressure inside the furnace to 3×10^(-3)Pa.

[0030] ③ Start the electromagnetic induction heating system to heat and melt the raw materials, control the heating rate and melting temperature, raise the temperature in the furnace to 1450°C at a heating rate of 6°C per minute, and the melting time is 1.2 hours to avoid local overheating of the raw materials or thermal stress due to too rapid heating.

[0031] ④ During the smelting process, electromagnetic stirring is used with a stirring frequency of 25 Hz, a stirring intensity of 0.1 T and a stirring time of 40 minutes to fully mix the alloy liquid, homogenize the alloy composition, and promote the floating and discharge of gas and inclusions.

[0032] ⑤ Prepare electroslag, the composition and proportion of electroslag are: 45% calcium oxide, 25% aluminum oxide, 18% magnesium oxide, 12% calcium fluoride. Dry the electroslag raw materials and crush them to a particle size of about 0.8 mm.

[0033] ⑥ Cast the vacuum-melted alloy liquid into a consumable electrode with a diameter of 70 mm and a length of 700 mm. Insert the consumable electrode into the slag of the electroslag remelting furnace and pass a current of 2500A for remelting. Under the action of the current, the consumable electrode gradually melts, and the molten metal droplets pass through the slag layer and solidify into ingots in the bottom crystallizer. The remelting rate is 7 kg per hour and the cooling rate is 7°C per minute, which improves the solidification structure of the alloy and reduces the formation of segregation and inclusions.

[0034] During the casting and cooling process, argon with a purity of 99.999% is introduced into the equipment and mold through the argon supply system. Multiple argon nozzles are set above and around the casting mold. The angle of the nozzle is 40°. The argon flow rate is controlled to 25 liters per minute and the argon pressure is 0.15MPa.

[0035] The beneficial effects of the present invention are that the gas impurities in the nickel-based high-temperature alloy are effectively removed, the removal effect of non-metallic inclusions is also very obvious, the low-melting-point metal impurities and other trace impurities are effectively removed, the purity and uniformity of the alloy are improved, the high-temperature strength is significantly improved, the tensile strength and yield strength of the alloy are improved, it can withstand a larger load, the application reliability is improved, and the oxidation resistance and corrosion resistance are improved. The oxidation rate of the alloy in a high-temperature oxidation environment is significantly reduced, the corrosion resistance is enhanced, the microstructure of the alloy is more uniform, the mechanical properties and thermal stability of the alloy are improved, the service life is extended, the process stability and reliability are high, the quality of the alloy is stable, and it is suitable for various types of nickel-based high-temperature alloys to achieve a better purification effect.

[0036] The above embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention. The protection scope of the present invention is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present invention.

Claims

1. A purification smelting method for a nickel-based high-temperature alloy, comprising the following steps: ① Raw material screening: select high-purity raw materials of main alloy elements such as nickel, chromium, molybdenum, cobalt, etc., requiring the purity of each element to reach a certain level of more than 99.9%, and pre-treat its surface; ② Select a vacuum induction melting furnace and perform vacuum treatment to reduce the pressure in the furnace to below 10^(-3)Pa; ③ Add the pretreated raw materials into the vacuum induction melting furnace in order, heat and melt the raw materials, and strictly control the heating rate and melting temperature; ④ Perform electromagnetic stirring, the frequency of electromagnetic stirring is controlled at 10Hz to 50Hz, and the stirring intensity is controlled at a magnetic field strength range of 0.05T to 0.2T, so that the alloy liquid is fully mixed, the alloy composition is homogenized, and the floating and discharge of gas and inclusions are promoted. The stirring time is 30 minutes to 1 hour; ⑤ Prepare special electroslag, dry and crush the prepared electroslag raw materials, control the drying temperature at 200℃ to 300℃, and continue for 6 to 8 hours. After drying, crush the electroslag raw materials to a particle size of 0.5 mm to 2 mm; ⑥ Cast the alloy liquid after vacuum melting into a consumable electrode, insert it into the slag of the electroslag remelting furnace and pass an electric current. Under the action of the electric current, the consumable electrode gradually melts, and the molten metal droplets pass through the slag layer and solidify into an ingot in the bottom crystallizer. The remelting rate is 5 to 10 kg per hour, and the cooling rate is 5°C to 10°C per minute to improve the solidification structure of the alloy and reduce the formation of segregation and inclusions.

2. A purification smelting method for nickel-based high-temperature alloy according to claim 1, characterized in that: In the step ①, the raw material is surface treated by combining mechanical grinding and chemical cleaning. After mechanical grinding to remove the oxide scale and rust on the surface, the raw material is soaked for 30 minutes to 1 hour. The cleaned raw material is rinsed with deionized water for multiple times until the resistivity of the rinse water reaches 18.2 MΩ·cm or more, so as to ensure that the cleaning liquid and impurities on the surface are completely removed.

3. A purification smelting method for nickel-based high-temperature alloy according to claim 2, characterized in that: The rinsed raw materials are dried at 80°C to 120°C until the surface of the raw materials is dry and no moisture remains.

4. A purification smelting method for nickel-based high-temperature alloy according to claim 1, characterized in that: In the step ③, the amount of nickel added is 50% to 60% of the total weight, and the amount of chromium added is 20% to 30%.

5. A purification smelting method for nickel-based high-temperature alloy according to claim 4, characterized in that: The heating rate in step ③ is generally controlled at 5°C to 10°C per minute to avoid local overheating of the raw materials or thermal stress due to too fast heating. The melting temperature is between 1400°C and 1600°C.

6. A purification smelting method for nickel-based high-temperature alloy according to claim 1, characterized in that: The content of calcium oxide in the electroslag prepared in step ⑤ is controlled to be 40% to 60%, and the content of aluminum oxide is 10% to 30%.

7. A purification smelting method for nickel-based high-temperature alloy according to claim 1, characterized in that: In step ⑥, the diameter of the consumable electrode is 50 mm to 100 mm, the length is 500 mm to 1000 mm, and the current passing through the consumable electrode is 1000A to 5000A.

8. A purification smelting method for nickel-based high-temperature alloy according to claim 1, characterized in that: In the step ⑥, argon gas is introduced into the smelting equipment and the casting mold through the gas supply pipe and the nozzle, so that the argon gas is isolated from the air and prevents the alloy from coming into contact with the air at high temperature and reacting.