Smelting method of high-temperature-resistant nickel-based alloy containing rare earth element yttrium

Abstract

The invention belongs to the technical field of smelting for producing high-aluminum and high-nickel nickel-based alloys in metallurgy and machinery industries, particularly relates to a smelting method of a high-temperature-resistant nickel-based alloy containing rare earth yttrium element, consists of two processes of vacuum induction smelting and vacuum consumable remelting, and relates to two devices of a vacuum induction furnace and a vacuum consumable furnace. According to the method, firstly, target values of elements such as C, Cr, Fe, Al, Si, Zr and Ti are accurately controlled, and particularly, the C (carbon) element is strictly controlled according to the lower limit; secondly, the vacuum degree in the smelting process is strictly controlled, and the content of gas elements such as H, O and N in metal is accurately controlled; and parameters such as stirring time and pouring temperature in vacuum smelting are strictly controlled again, so that the burning loss amount of the metal yttrium is accurately controlled, and the technical requirements of chemical components of 602CA are met. By optimizing technological parameters, the problem that metal yttrium is extremely prone to burning loss in the smelting process is solved, the smelting qualification rate of 602CA finished steel ingots is increased, and the production cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of smelting technology for high-aluminum and high-nickel nickel-based alloys in the metallurgical and machinery industries. In particular, it relates to a method for smelting high-temperature resistant nickel-based alloys containing rare earth yttrium, which is especially suitable for high-temperature resistant materials in the fields of metal heat treatment and chemical production. Background Technology

[0002] Nickel-based alloys are generally defined as alloys with a Ni content exceeding 30 wt%, with common nickel-based alloys having a Ni content exceeding 50 wt%. Due to their superior high-temperature mechanical strength and corrosion resistance, they are collectively referred to as superalloys along with iron-based and cobalt-based alloys. They are typically used in high-temperature environments above 540°C. Nickel-based alloys exhibit high strength and a certain degree of resistance to oxidation and corrosion at temperatures ranging from 650 to 1000°C. Based on their main properties, they are classified into: nickel-based heat-resistant alloys, nickel-based corrosion-resistant alloys, nickel-based wear-resistant alloys, nickel-based precision alloys, and nickel-based shape memory alloys. Different alloy designs are selected according to their application, and they are often used in special corrosion-resistant environments, high-temperature corrosive environments, and equipment requiring high-temperature mechanical strength. They are commonly used in aerospace, energy, petrochemical industries, and specialized electronics / optoelectronics fields.

[0003] Rare earth elements, often referred to as "industrial gold," possess excellent photoelectric and electromagnetic properties, enabling them to combine with other materials to form a wide variety of new materials with diverse properties. The most significant function of rare earth elements is their ability to substantially improve the quality and performance of other products. Rare earth elements are also a key mineral resource in China. In the metallurgical industry, adding rare earth elements to steel can refine, desulfurize, neutralize low-melting-point harmful impurities, improve the processing performance of steel, enhance the physicochemical properties of steel and non-ferrous alloys, and improve the room-temperature and high-temperature mechanical properties of alloys.

[0004] Grade 602CA (UNS N06025) is a newly developed nickel-based alloy material in recent years. It belongs to the nickel-chromium-iron carbide-reinforced heat-resistant nickel-based alloy category and has excellent high-temperature performance and superior corrosion resistance. 602CA (UNS N06025) is mainly composed of nickel, chromium, iron, and aluminum, with trace amounts of carbon, titanium, praseodymium, zirconium, and yttrium added. The interaction of these elements results in a face-centered cubic (FCC) crystal structure, which endows the alloy with good oxidation resistance, corrosion resistance, high-temperature strength, and thermal stability under high-temperature environments.

[0005] The main components of 602CA (UNS N06025) include: C = 0.15-0.25%, Ni = balance, Cr = 24-26%, Fe = 8-11%, Al = 1.8-2.4%, Si ≤ 0.5%, Zr = 0.01-0.1%, Y = 0.05-0.12%, etc.

[0006] Due to the beneficial effects of high carbon, high chromium, high aluminum, and microalloying of titanium, zirconium, and yttrium, 602CA (UNS N06025) alloy possesses excellent resistance to high-temperature oxidation, good high-temperature strength, and excellent resistance to carburization and grain growth. It is widely used in basic equipment in aerospace, energy, chemical and other fields, such as heat treatment furnaces, furnace rollers, bright annealing hoods, calcining furnaces and other equipment.

[0007] Generally, nickel-based superalloys are smelted using vacuum induction remelting followed by electroslag remelting or vacuum induction remelting followed by vacuum arc remelting. The yttrium content of the 602CA (UNS N06025) alloy is 0.05%-0.12%. Because metallic yttrium is extremely prone to burn-off during the smelting process, traditional nickel-based alloy smelting processes cannot meet the technical requirements for yttrium smelting, and metallic yttrium is crucial to the performance of 602CA (UNS N06025).

[0008] Yttrium, with the chemical symbol Y, is a dark gray metal and the first rare earth element discovered. It is malleable, reacts with hot water, and is readily soluble in dilute acids. It is commonly used in specialty glasses and metal alloys. Industrially used yttrium typically has a purity of no less than 93.4%. However, yttrium is prone to oxidation loss during high-temperature smelting, making it a technical challenge in the smelting of yttrium-containing metals.

[0009] Due to the properties of yttrium, it poses a challenge to the industrial mass production of yttrium-containing nickel-based alloys. Employing a vacuum smelting process can effectively improve the stability of yttrium during high-temperature smelting, requiring a dual-vacuum smelting method: vacuum induction followed by vacuum arc remelting. Because the industrial production of rare earth elements is cutting-edge technology, it is considered core technology internationally and is not subject to disclosure. Therefore, smelting technologies involving 602CA (UNS N06025) have been subject to technological embargoes internationally, with few public reports and no relevant domestic data available for reference.

[0010] In recent years, with the gradual development of related domestic industries, the demand for 602CA (UNS N06025) nickel-based alloy materials has increased dramatically. However, foreign monopolies and technological barriers have, to some extent, constrained the orderly development of related domestic industries. Therefore, this study focuses on tackling key technical challenges in the smelting process of 602CA (UNS N06025) nickel-based alloy. Utilizing existing smelting equipment, a dual-vacuum (vacuum induction + vacuum consumable remelting) process is adopted. By optimizing and controlling parameters such as the timing and quantity of yttrium addition during the smelting process, the technical requirements for the industrial mass production of this alloy are met. This will enable the domestic mass production of this grade of nickel-based alloy containing the rare earth element yttrium, ensuring the security and stability of the supply chain for related industries. Summary of the Invention

[0011] The purpose of this invention is to design and develop a smelting method for high-temperature resistant nickel-based alloys containing the rare earth element yttrium. The method comprises two processes: vacuum induction smelting and vacuum arc remelting, involving both a vacuum induction furnace and a vacuum arc remelting furnace. Firstly, this invention precisely controls the target values ​​of elements such as C, Cr, Fe, Al, Si, Zr, and Ti, especially strictly controlling C (carbon) to the lower limit. Secondly, it employs strict control of the vacuum level during the smelting process to precisely control the content of gaseous elements such as H, O, and N in the metal. Thirdly, it strictly controls parameters such as stirring time and pouring temperature during vacuum smelting to precisely control the yttrium loss, meeting the chemical composition technical requirements of 602CA. This invention features a reasonable process. Based on the elemental composition requirements of nickel-chromium-iron-based carbide-reinforced heat-resistant nickel-based alloys, it rationally sets internal control components, target components, and operational points, enabling the smelting of 602CA finished steel ingots that meet technical requirements. This breaks down industry technical barriers, facilitates the domestic industrial mass production of this product, and promotes the orderly development of related domestic industries. By optimizing process parameters, the problem of yttrium's susceptibility to burn-off during smelting is overcome, improving the smelting qualification rate of 602CA steel ingots and reducing production costs. The adoption of a dual-vacuum smelting process is green and low-carbon, reducing pollutant emissions and offering significant social benefits. It also shows promising market prospects for the application of vacuum smelting technology in high-temperature nickel-based alloys within the industry.

[0012] To achieve the above objectives, the technical solution of this invention is as follows:

[0013] A method for smelting a high-temperature nickel-based alloy containing the rare earth element yttrium is characterized by: vacuum induction smelting and vacuum arc remelting. First, the target values ​​of elements C, Si, Mn, P, S, Cr, Ni, Cu, Al, Ti, Fe, Zr, and Y are precisely controlled, especially the C (carbon) element, which is strictly controlled to the lower limit, specifically between 0.15% and 0.18%. Second, the vacuum degree during the smelting process is strictly controlled to achieve precise control of the content of gaseous elements such as H, O, and N in the metal. Third, parameters such as stirring time and pouring temperature during vacuum smelting are strictly controlled to precisely control the yttrium loss and meet the chemical composition technical requirements of 602CA.

[0014] Furthermore, the vacuum induction smelting process specifically includes: material preparation → charging → pre-vacuuming → melting → vacuum preparation → melt cleaning → film formation, adding Al and Ti → taking pre-furnace samples → adjusting composition → taking finished product samples → purging with argon and adding metallic yttrium → casting φ360-430mm electrodes → inspection and warehousing.

[0015] Pre-vacuuming: After the furnace is closed after charging, a pre-vacuuming is performed with a vacuum degree ≤10Pa;

[0016] The melting process involves: pre-vacuuming to ≤10Pa, then powering on the induction furnace and heating the crucible to a power not exceeding 250KW to melt the loaded material. After melting, the material is stirred at a melt temperature of 1440-1530℃ for at least 5 minutes using electromagnetic stirring.

[0017] The vacuum preparation involves continuously drawing a vacuum, with a vacuum degree ≤ 2.7 Pa.

[0018] The melting process is as follows: when the vacuum degree of the induction furnace reaches ≤2.7Pa, the power is increased to 1200KW; the melting temperature is controlled at 1490-1510℃, and the vacuum degree is not greater than 2.7Pa.

[0019] The film formation process involves: when the induction furnace is powered off, gas is introduced to form a film on the surface of the high-temperature liquid after melting and clearing; then alloy materials such as Al and Ti are added according to the specified ratio.

[0020] The adjusted composition: Based on the results of the pre-furnace chemical composition test, the composition is adjusted, and Zr alloy material is added according to the ratio;

[0021] Argon purging and yttrium addition: after purging with argon, yttrium is added at a rate of 0.50% to 0.60% wt, and the stirring time after adding yttrium is no more than 5 minutes;

[0022] The φ360-430 electrode is a solution-cast electrode rod in an induction furnace, with a casting temperature of 1440-1530℃.

[0023] Furthermore, the material preparation is based on the requirements of smelting technology; the material is pure iron, yttrium, chromium, titanium, zirconium, crystalline silicon or nickel plate, and the content of each of the above elements is above 99%.

[0024] Furthermore, the loading process involves hoisting the prepared materials into the crucible in batches.

[0025] Furthermore, the pre-furnace sample taking involves taking a sample inside the furnace through a sampling window and performing chemical composition analysis.

[0026] Furthermore, the pre-furnace sample taking process involves: purging with argon and adding metallic yttrium, purging with argon gas, re-introducing high-purity argon gas into the vacuum chamber, with an argon gas strength of 15000-25000 Pa; molten steel temperature of 1500-1520℃; and a holding time of 5-10 minutes.

[0027] Furthermore, the argon purging and yttrium addition are followed by a stirring time of 2-3 minutes after the yttrium is added.

[0028] Furthermore, the vacuum self-consumption smelting specifically includes: material preparation (φ360-430mm electrode rod) → cutting and peeling → welding auxiliary electrode → vacuuming → detecting leakage rate → vacuum self-consumption smelting (until the electrode is completely melted) → cooling → demolding → turning → inspection → warehousing.

[0029] Material preparation: finished electrode rods with a diameter of φ360-430mm, produced by vacuum induction casting;

[0030] The welding auxiliary electrode has a welding current of 160-220A, a welding voltage of 20-25V, and a shielding gas ratio of 80% Ar + 20% CO2.

[0031] The vacuum level before arc initiation is ≤1.33 Pa;

[0032] The leak rate was measured using a vacuum gauge and was ≤0.133 Pa / min.

[0033] The self-consumable smelting process involves remelting in a 5-ton vacuum self-consumable furnace with a melting rate set at 2.7-3.7 kg / min and a voltage set at 23V. The metal is then melted by energizing the furnace.

[0034] The cooling process involves: first, furnace cooling for ≥60 minutes, followed by air cooling after ingot removal.

[0035] Furthermore, the cutting and peeling process involves using a machine tool for overall cutting or a grinding machine to cut and grind the outer circumference and end face of the φ360-430mm electrode rod. The grinding amount should be no less than 3mm, and the metallic luster of the electrode rod surface should be visible after cutting and grinding.

[0036] Furthermore, the welding auxiliary electrode can be used for welding methods such as manual arc welding, tungsten inert gas welding (TIG welding), and gas metal arc welding (MIG / MAG welding); the MIG welding material is φ1.2mm stainless steel welding wire. Detailed description of the invention:

[0038] This invention provides a smelting method for high-temperature nickel-based alloys containing the rare earth element yttrium. This is the first development of nickel-based high-temperature alloy steel ingots in China. It consists of two processes: vacuum induction smelting and vacuum arc remelting, involving two types of equipment: a vacuum induction furnace and a vacuum arc remelting furnace.

[0039] 1. Vacuum induction process

[0040] The vacuum induction process involves smelting relevant raw materials under vacuum conditions using induction. Its function is to melt recycled materials of the same steel grade, metallic Cr, Ni, and other raw materials in a vacuum environment, add elements such as Ti, Y, and Al for micro-alloying, and then cast them into electrodes (rods) with a diameter of φ360-430mm.

[0041] The technical characteristics of the vacuum induction process are as follows: First, precise control of the composition of C, Si, Mn, P, S, Cr, Ni, Cu, Al, Ti, Fe, Zr, and Y to achieve the target values ​​in Table 1; second, strict control of the content of gases such as H, O, and N in the molten metal (on the one hand, by carefully selecting raw materials; on the other hand, by ensuring that electro-smelting can only be carried out when the vacuum degree is no greater than 2.7 Pa); and third, control of parameters such as pouring temperature and stirring time to control the burn-off of yttrium. Specifically, the critical yttrium is added according to 80%–90% of the burn-off amount, i.e., at a calculated amount of 0.50%–0.60%.

[0042] The process includes: material preparation → loading → pre-vacuuming → melting → vacuum preparation → melt cleaning → film formation, adding Al and Ti → taking pre-furnace samples → adjusting composition → taking finished product samples → argon purging and adding metallic yttrium → casting φ360-430mm electrodes → inspection and warehousing, etc. (see appendix for details) Figure 1 (Vacuum induction smelting curve).

[0043] 1) Material preparation: Prepare the corresponding materials according to the smelting technology requirements (e.g., target values ​​for each element, whether to use metal or recycled material of the same steel grade as the raw material, and the baking of the raw material). The specific materials include: pure iron, yttrium metal, chromium metal, titanium metal, zirconium metal, crystalline silicon, and nickel plate. The content of each of the above elements is above 99%. The combination of recycled material of the same steel grade or similar steel grade with alloy can be used.

[0044] 2) Charging: The prepared materials are hoisted into the crucible in batches (according to weight, about 1000 kg is loaded each time, and the next batch is loaded after melting) and filled into place (mainly referring to the ladle capacity, the furnace loading amount is about 4700 kg).

[0045] 3) Pre-vacuuming: After the furnace is closed after charging, pre-vacuuming should be carried out, with the vacuum degree ≤10Pa.

[0046] 4) Melting: After pre-vacuuming to ≤10Pa, the induction furnace is powered on and the crucible is heated. The power should not exceed 250KW to melt the filled material. After melting, the melt is stirred to ensure uniformity. At this time, the melt temperature is controlled at 1440-1530℃, and electromagnetic stirring is performed for at least 5 minutes.

[0047] 5) Vacuum preparation: Turn on the vacuum pump (such as a Roots pump) of the vacuum induction system to continuously draw a vacuum, preferably with a vacuum degree ≤2.7Pa.

[0048] 6) Melting and Clearing: Once the vacuum degree of the induction furnace reaches ≤2.7Pa, it is advisable to increase the power to 1200KW to ensure the material in the crucible melts and clears completely. The melting and clearing temperature should be controlled at 1490-1510℃, and the vacuum degree should not exceed 2.7Pa.

[0049] 7) Film formation: After the induction furnace is powered off, an air-filled film is formed on the surface of the high-temperature liquid after melting and clearing to prevent defects such as slurry stirring, tanning, top expansion, and shell sticking, and to ensure vacuum. Then Al and Ti are added according to the formula.

[0050] 8) Sample taking before furnace: Take samples inside the furnace through the sampling window and perform chemical composition analysis.

[0051] 9) Adjust composition: Adjust the composition according to the chemical composition test results before the furnace, and add Zr metal according to the ratio (target value of Zr element 0.06%wt).

[0052] 10) Take a sample of the finished product: Take a sample in the furnace through the sampling window and perform chemical composition analysis. If it meets the technical requirements, proceed to the next step. If it does not meet the requirements, readjust the composition or scrap the product.

[0053] 11) Argon purging and yttrium addition: After the finished sample meets the requirements (Table 1, internal control values), purge with argon (high-purity argon is reintroduced into the vacuum chamber. The operation should be carried out strictly in accordance with the specified argon pressure, molten steel temperature, and holding time (argon intensity: 15000-25000 Pa; molten steel temperature: 1500-1520℃; holding time: 5-10 minutes). After purging with argon, add yttrium. The amount added should be 0.50% to 0.60% of the calculated amount. The stirring time after adding yttrium should be controlled to not exceed 5 minutes, especially 2-3 minutes.

[0054] 12) Casting φ360-430 electrodes: The electrode rods are cast in the solution in the induction furnace. The casting temperature should be 50-80℃ above the liquid phase temperature, that is, the casting temperature should be controlled at 1440-1530℃, especially 1510±10℃.

[0055] 13) Inspection and warehousing: After the electrode rods have cooled, inspect their external dimensions (electrode size: φ360-430mm) according to the technical requirements, and take samples for testing (see Table 1 for details). After passing the test, they will be stored in the warehouse.

[0056] Table 1: Composition Control in Vacuum Induction Smelting

[0057]

[0058] 2. Vacuum self-consuming process

[0059] The vacuum consumable electrode remelting process involves a secondary vacuum smelting of vacuum-induction-formed electrodes (rods) under vacuum conditions using a consumable remelting method. Its functions are: 1) To remelt, degas, and cast φ360-430mm electrodes into φ420-510mm steel ingots in a vacuum environment. 2) To control the vacuum level and leakage rate; the vacuum level before arc ignition should ideally not exceed 1.33Pa, and the leakage rate should ideally not exceed 0.133Pa / min. 3) To control the melting rate during the smelting process to 2.7-3.7 kg / min.

[0060] Technical characteristics of vacuum arc remelting process: Steel ingots after vacuum arc remelting have higher purity, lower gas content, less yttrium loss during smelting, and the chemical composition of finished steel ingots meets standard requirements.

[0061] The vacuum consumable electrode process includes: material preparation (φ360-430mm electrode rod) → cutting and peeling → welding auxiliary electrodes → vacuuming → leak rate detection → vacuum consumable smelting (until the electrode is completely melted) → cooling → demolding → turning → inspection → warehousing, etc.

[0062] 1) Material preparation: Take out the finished φ360-430mm electrode rods from the warehouse and check the external dimensions and other parameters according to the technical requirements. They must meet the process technical requirements.

[0063] 2) Cutting and peeling: The outer circumference and end face of the φ360-430mm electrode rod are cut and ground by machine tool or by grinding machine. The grinding amount should be no less than 3mm, and the metallic luster of the electrode rod surface should be visible after cutting and grinding.

[0064] 3) Welding auxiliary electrodes: Welding methods include manual arc welding, tungsten inert gas welding (TIG welding), and gas metal arc welding (MIG / MAG welding). The MIG welding material is φ1.2mm stainless steel welding wire. The welding current is 160-220A, the welding voltage is 20-25V, and the shielding gas composition is 80% Ar + 20% CO2.

[0065] 4) Vacuuming: Use a vacuum pump to evacuate the vacuum, and the vacuum level before arc initiation should be ≤1.33Pa.

[0066] 5) Leakage rate detection: Use a vacuum gauge for detection, and the actual measured leakage rate should be ≤0.133 Pa / min.

[0067] 6) Consumable metallurgy: A 5-ton vacuum consumable furnace is used for remelting. The melting rate is set to 2.7-3.7 kg / min and the voltage is set to 23V. The metal is melted by turning on the power.

[0068] 7) Cooling: First, cool with the furnace, preferably for ≥60 minutes, then remove the ingot and cool in the sheltered air.

[0069] 8) Demolding: This refers to removing the self-consumable smelted steel ingot from the ingot mold.

[0070] 9) Turning: The end face and outer circumferential surface of the φ420-510mm consumable ingot are machined by lathe according to the process requirements. The cutting amount is preferably 3-5mm.

[0071] 10) Inspection: Use a hand drill to collect chip samples from the consumable ingot and test their chemical composition;

[0072] 11) Warehousing: After passing the chemical composition and surface inspection, the product is put into storage.

[0073] According to the aforementioned dual-vacuum production process, the smelting precision of yttrium can be effectively controlled, with the yttrium content controlled at 0.10%, and steel ingots that meet the standard requirements can be obtained.

[0074] Beneficial technical effects

[0075] 1) The process is reasonable. Based on the elemental composition requirements of nickel-chromium-iron-based carbide-reinforced heat-resistant nickel-based alloys, the internal control composition, target composition, and key operating points are reasonably set to improve the smelting qualification rate of 602CA finished steel ingots; (the current qualification rate is...)

[0076] 100%

[0077] 2) By precisely controlling the target values ​​of C, Si, Mn, P, S, Cr, Ni, Cu, Al, Ti, Fe, Zr, and Y elements, especially strictly controlling the C (carbon) element according to the lower limit, the composition is guaranteed to meet the standards;

[0078] 3) By strictly controlling the vacuum level during the smelting process, the content of gaseous elements such as H, O, and N in the metal can be precisely controlled;

[0079] 4) Strictly control parameters such as stirring time and pouring temperature in vacuum smelting to accurately control the amount of yttrium loss and overcome the problem that yttrium is easily burned off during the smelting process;

[0080] 5) Breaking through industry technical barriers, achieving the first smelting in China, helping the domestic industrial mass production of this product, and promoting the orderly development of related domestic industries;

[0081] 6) The adoption of a dual-vacuum smelting process is green and low-carbon, reducing pollutant emissions and having good social benefits. It also has a good market prospect for the application of vacuum smelting technology for high-temperature nickel-based alloys in the industry. Attached Figure Description

[0082] Figure 1 Vacuum induction smelting curve.

[0083] Figure 2 Vacuum induction smelting process flow diagram.

[0084] Figure 3 Vacuum self-consumable smelting process flow diagram. Detailed Implementation

[0085] The technical solution of the present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are only used to describe the specific implementation of the present invention and are not intended to constitute any limitation on the scope of protection of the present invention.

[0086] A steel company in Shanghai has used this invention on its special alloy smelting production line to industrially produce 602CA nickel-chromium-iron-based carbide-reinforced heat-resistant nickel-based alloy steel ingots with specifications of φ423-510mm, thus realizing the domestic industrial production of this type of heat-resistant nickel-based alloy steel ingot.

[0087] This invention provides a method for smelting nickel-based alloys containing the rare earth element yttrium. It is the first development of a heat-resistant nickel-based alloy strengthened by nickel-chromium-iron carbides. The method is characterized by consisting of two processes: vacuum induction smelting and vacuum arc remelting, involving two types of equipment: a vacuum induction furnace and a vacuum arc remelting furnace.

[0088] 1. Vacuum induction process

[0089] The vacuum induction process involves smelting relevant raw materials under vacuum conditions using induction. Its function is to melt recycled materials of the same steel grade, metallic Cr, Ni, and other raw materials in a vacuum environment, add elements such as Ti, Y, and Al for micro-alloying, and then cast them into electrodes (rods) with a diameter of φ360-430mm.

[0090] The technical characteristics of the vacuum induction process are as follows: First, precise control of the composition of C, Si, Mn, P, S, Cr, Ni, Cu, Al, Ti, Fe, Zr, and Y to achieve the target values ​​in Table 1; second, strict control of the content of gases such as H, O, and N in the molten metal (on the one hand, by carefully selecting raw materials; on the other hand, by ensuring that electro-smelting can only be carried out when the vacuum degree is no greater than 2.7 Pa); and third, control of parameters such as pouring temperature and stirring time to control the burn-off of yttrium. Specifically, the critical yttrium is added according to 80%–90% of the burn-off amount, i.e., at a calculated amount of 0.50%–0.60%.

[0091] The process includes: material preparation → loading → pre-vacuuming → melting → vacuum preparation → melt cleaning → film formation, adding Al and Ti → taking pre-furnace samples → adjusting composition → taking finished product samples → argon purging and adding metallic yttrium → casting φ360-430mm electrodes → inspection and warehousing, etc. (see appendix for details) Figure 1 (Vacuum induction smelting curve).

[0092] 1) Material preparation: Prepare the corresponding materials according to the smelting technology requirements (e.g., target values ​​for each element, whether to use metal or recycled material of the same steel grade as the raw material, and the baking of the raw material). The specific materials include: pure iron, yttrium metal, chromium metal, titanium metal, zirconium metal, crystalline silicon, and nickel plate. The content of each of the above elements is above 99%. The combination of recycled material of the same steel grade or similar steel grade with alloy can be used.

[0093] 2) Charging: The prepared materials are hoisted into the crucible in batches (according to weight, about 1000 kg is loaded each time, and the next batch is loaded after melting) and filled into place (mainly referring to the ladle capacity, the furnace loading amount is about 4700 kg).

[0094] 3) Pre-vacuuming: After the furnace is closed after charging, pre-vacuuming should be carried out, with the vacuum degree ≤10Pa.

[0095] 4) Melting: After pre-vacuuming to ≤10Pa, the induction furnace is powered on and the crucible is heated. The power should not exceed 250KW to melt the filled material. After melting, the solution is stirred to ensure uniformity. At this time, the temperature of the melt is controlled at 1490-1510℃, and the electromagnetic stirring is carried out for at least 3 minutes.

[0096] 5) Vacuum preparation: Turn on the vacuum pump (such as a Roots pump) of the vacuum induction system to continuously draw a vacuum, preferably with a vacuum degree ≤2.7Pa.

[0097] 6) Melting and clearing: Once the vacuum degree of the induction furnace reaches the requirement of ≤2.7Pa, it is advisable to adjust the power to increase to 1200KW to ensure that the material in the crucible is melted and cleared.

[0098] 7) Film formation: After the induction furnace is powered off, an air-filled film is formed on the surface of the high-temperature liquid after melting and clearing to prevent defects such as slurry, tanning, top expansion, and shell sticking, and to ensure the vacuum degree. Then, alloy materials such as Al and Ti are added according to the formula.

[0099] 8) Sample taking before furnace: Take samples inside the furnace through the sampling window and perform chemical composition analysis.

[0100] 9) Adjust composition: Adjust the composition according to the chemical composition test results before the furnace, and add Zr metal according to the ratio (target value of Zr element 0.06%wt).

[0101] 10) Take a sample of the finished product: Take a sample in the furnace through the sampling window and perform chemical composition analysis. If it meets the technical requirements, proceed to the next step. If it does not meet the requirements, readjust the composition or scrap the product.

[0102] 11) Argon purging and addition of yttrium: After the finished sample meets the requirements (Table 1, internal control values), purge with argon (high-purity argon is reintroduced into the vacuum chamber. The operation should be strictly carried out according to the specified argon pressure, molten steel temperature, and holding time. Argon intensity: 15000-25000 Pa; molten steel temperature: 1500-1520℃; holding time: 5-10 minutes). After purging with argon, add yttrium. The amount added should be 0.50% to 0.60% of the calculated amount. The stirring time after adding yttrium should be controlled to not exceed 5 minutes, especially 2-3 minutes.

[0103] 12) Casting φ360-430 electrodes: The electrode rods are cast in the solution in the induction furnace. The casting temperature should be 50-80℃ above the liquid phase temperature, that is, the casting temperature should be controlled at 1440-1530℃, especially 1510±10℃.

[0104] 13) Inspection and warehousing: After the electrode rods have cooled, inspect their external dimensions (electrode size: φ360-430mm) according to the technical requirements, and take samples for testing (see Table 1 for details). After passing the test, they will be stored in the warehouse.

[0105] 2. Vacuum self-consuming process

[0106] The vacuum consumable electrode remelting process involves secondary vacuum smelting of vacuum-induction-formed electrodes (rods) under vacuum conditions using a consumable remelting method. Its functions are: 1) To remelt, degas, and cast φ360-430mm electrodes into φ423-510mm steel ingots in a vacuum environment. 2) To control the vacuum level and leakage rate; the vacuum level before arc ignition should ideally not exceed 1.33Pa, and the leakage rate should ideally not exceed 0.133Pa / min. 3) To control the melting rate during the smelting process to 2.7-3.7 kg / min.

[0107] Technical characteristics of vacuum arc remelting process: Steel ingots after vacuum arc remelting have higher purity, lower gas content, less yttrium loss during smelting, and the chemical composition of finished steel ingots meets standard requirements.

[0108] The vacuum consumable electrode process includes: material preparation (φ360-430mm electrode rod) → cutting and peeling → welding auxiliary electrodes → vacuuming → leak rate detection → vacuum consumable smelting (until the electrode is completely melted) → cooling → demolding → turning → inspection → warehousing, etc.

[0109] 1) Material preparation: Take out the finished φ360-430mm electrode rods from the warehouse and check the external dimensions and other parameters according to the technical requirements. They must meet the process technical requirements.

[0110] 2) Cutting and peeling: The outer circumference and end face of the φ360-430mm electrode rod are cut and ground by machine tool or by grinding machine. The grinding amount should be no less than 3mm, and the metallic luster of the electrode rod surface should be visible after cutting and grinding.

[0111] 3) Welding auxiliary electrode: Welding methods include manual arc welding, tungsten inert gas welding (TIG welding), and gas metal arc welding (MIG / MAG welding). The MIG welding material is φ1.2mm stainless steel welding wire. The welding current is 160-220A, the welding voltage is 20-25V, and the shielding gas composition is 80% Ar + 20% CO2.

[0112] 4) Vacuuming: Use a vacuum pump to evacuate the vacuum, and the vacuum level before arc initiation should be ≤1.33Pa.

[0113] 5) Leakage rate detection: Use a vacuum gauge for detection, and the actual measured leakage rate should be ≤0.133 Pa / min.

[0114] 6) Consumable metallurgy: A 5-ton vacuum consumable furnace is used for remelting. The melting rate is set to 2.7-3.7 kg / min and the voltage is set to 23V. The metal is melted by turning on the power.

[0115] 7) Cooling: First, cool with the furnace, preferably for ≥60 minutes, then remove the ingot and cool in the sheltered air.

[0116] 8) Demolding: This refers to removing the self-consumable smelted steel ingot from the ingot mold.

[0117] 9) Turning: The end face and outer circumferential surface of the φ423-510mm consumable ingot are machined by lathe according to the process requirements. The cutting amount is preferably 3-5mm.

[0118] 10) Inspection: Use a hand drill to collect chip samples from the consumable ingot and test their chemical composition;

[0119] 11) Warehousing: After passing the chemical composition and surface inspection, the product is put into storage.

[0120] According to the aforementioned dual-vacuum production process, the smelting precision of yttrium can be effectively controlled, with the yttrium content controlled at 0.10%, and steel ingots that meet the standard requirements can be obtained.

[0121] A method for smelting a high-temperature resistant nickel-based alloy containing the rare earth element yttrium involves three key steps. First, precise control of target values ​​for elements such as C, Cr, Fe, Al, Si, Zr, and Ti is employed, with C (carbon) strictly controlled to the lower limit. Second, strict control of the vacuum level during the smelting process ensures precise control of the content of gaseous elements such as H, O, and N in the metal. Third, strict control of parameters such as stirring time and pouring temperature during vacuum smelting ensures precise control of yttrium loss, meeting the chemical composition requirements of 602CA. The process is rationally designed, and based on the elemental composition requirements of nickel-chromium-iron carbide-reinforced heat-resistant nickel-based alloys, internal control components, target components, and operational points are rationally set. This method enables the first domestic smelting of 602CA finished steel ingots that meet the technical requirements, breaking through industry technical barriers, facilitating the domestic industrial mass production of this product, and promoting the orderly development of related domestic industries. By optimizing process parameters, the problem of yttrium's susceptibility to burn-off during smelting is overcome, improving the smelting qualification rate of 602CA steel ingots and reducing production costs, generating over one million yuan in economic value annually. The dual-vacuum smelting process is green and low-carbon, reducing pollutant emissions and offering significant social benefits. It also shows promising market prospects for the application of vacuum smelting technology in high-temperature nickel-based alloys within the industry. Specific implementation examples:

[0123] A steel company in Shanghai used this invention on a special alloy smelting production line. Taking a 602CA nickel-chromium-iron-based carbide-reinforced heat-resistant nickel-based alloy with a steel ingot diameter of φ423mm as an example, the invention applied a nickel-based alloy smelting method containing the rare earth element yttrium. This is the first development of a nickel-chromium-iron-based carbide-reinforced heat-resistant nickel-based alloy. The invention is characterized by consisting of two processes: vacuum induction smelting and vacuum arc remelting, involving two types of equipment: a vacuum induction furnace and a vacuum arc remelting furnace.

[0124] 1. Vacuum induction process

[0125] The vacuum induction process involves smelting relevant raw materials under vacuum conditions using induction. Its function is to melt recycled materials of the same steel grade, metallic Cr, Ni, and other raw materials in a vacuum environment, add elements such as Ti, Y, and Al for micro-alloying, and then cast them into φ360mm electrodes (rods).

[0126] The technical characteristics of the vacuum induction process are as follows: First, precise control of the composition of C, Si, Mn, P, S, Cr, Ni, Cu, Al, Ti, Fe, Zr, and Y to achieve the target values ​​in Table 1; second, strict control of the content of gases such as H, O, and N in the molten metal (on the one hand, by carefully selecting raw materials; on the other hand, by ensuring that electro-smelting can only be carried out when the vacuum degree is no greater than 2.7 Pa); and third, control of parameters such as pouring temperature and stirring time to control the burn-off of yttrium. Specifically, the critical yttrium is added according to 80%–90% of the burn-off amount, i.e., at a calculated amount of 0.50%–0.60%.

[0127] The process includes: material preparation → loading → pre-vacuuming → melting → vacuum preparation → melt cleaning → film formation, adding Al and Ti → taking pre-furnace samples → adjusting composition → taking finished product samples → argon purging and adding yttrium metal → casting φ360mm electrodes → inspection and warehousing, etc. (see appendix for details) Figure 1 (Vacuum induction smelting curve).

[0128] 1) Material preparation: According to the smelting technology requirements, the following materials are prepared: pure iron, yttrium metal, chromium metal, titanium metal, zirconium metal, crystalline silicon, and nickel plate. The content of each of the above elements is above 99%.

[0129] 2) Loading: The prepared materials are hoisted into the crucible in batches according to weight, with each batch weighing about 1000 kg. After melting, the next batch is loaded, with a total loading of 4700 kg.

[0130] 3) Pre-vacuuming: After the furnace is closed after charging, pre-vacuuming should be carried out, with a vacuum degree of 5-10 Pa being appropriate.

[0131] 4) Melting: After pre-vacuuming to ≤10Pa, the induction furnace is powered on and the crucible is heated. The power should not exceed 250KW to melt the filled material. After melting, the solution is stirred to ensure uniformity. At this time, the temperature of the melt is controlled at 1506℃, and electromagnetic stirring is performed for 5 minutes.

[0132] 5) Vacuum preparation: Turn on the vacuum pump (such as a Roots pump) of the vacuum induction system to continuously draw a vacuum, preferably with a vacuum degree ≤2.7Pa.

[0133] 6) Melting and Clearing: Once the vacuum degree of the induction furnace reaches ≤2.7Pa, it is advisable to increase the power to 1200KW to ensure the material in the crucible melts and clears completely. The melting and clearing temperature should be controlled at 1502℃, and the vacuum degree should not exceed 2.7Pa.

[0134] 7) Film formation: After the induction furnace is powered off, an air-filled film is formed on the surface of the high-temperature liquid after melting and clearing to prevent defects such as slurry, tanning, top expansion, and shell sticking, and to ensure the vacuum degree. Then, alloy materials such as Al and Ti are added according to the formula.

[0135] 8) Sample taking before furnace: Take samples inside the furnace through the sampling window and perform chemical composition analysis.

[0136] (C: 0.18%; Si: 0.26%; Mn: 0.03%; P: 0.004%; Cr: 24.81%; Fe: 10.08%; Al: 2.20%; Ti: 0.15%; Cu: 0.02%; Ni: 62.20%; S: 0.001%)

[0137] 9) Adjust the composition: Adjust the composition according to the chemical composition test results before the furnace, and add Zr alloy material according to the ratio.

[0138] 10) Take a sample of the finished product: Take a sample in the furnace through the sampling window and perform chemical composition analysis. If it meets the technical requirements, proceed to the next step. If it does not meet the requirements, readjust the composition or scrap the product.

[0139] 11) Argon purging and yttrium addition: After the finished sample meets the requirements, argon gas is purged (high-purity argon gas is reintroduced into the vacuum chamber, and the operation should be strictly carried out in accordance with the specified argon gas pressure, steel liquid temperature and holding time). After purging with argon gas, yttrium is added. The amount added should be 0.50% to 0.60% of the calculated amount. The stirring time after adding yttrium should be controlled to not exceed 5 minutes, especially 2-3 minutes.

[0140] 12) Casting φ360 electrode: Cast electrode rods in solution in induction furnace. The casting temperature should be 50-80℃ above the liquid phase temperature, that is, the casting temperature should be controlled at 1440-1530℃, especially 1510±10℃.

[0141] 13) Inspection and warehousing: After the electrode rods have cooled, inspect their external dimensions according to the technical requirements and take samples for testing (see Table 1 for details). Once qualified, they will be stored in the warehouse.

[0142] 2. Vacuum self-consuming process

[0143] The vacuum self-consumable melting process involves a secondary vacuum smelting of vacuum-induction-formed electrodes (rods) under vacuum conditions using a self-consumable remelting method. Its functions are: 1) To remelt, degas, and cast φ360mm electrodes into φ423mm steel ingots in a vacuum environment. 2) To control the vacuum level and leakage rate; the vacuum level before arc ignition should ideally not exceed 1.33Pa, and the leakage rate should ideally not exceed 0.133Pa / min. 3) To control the melting rate during the smelting process to 2.7-3.7 kg / min.

[0144] Technical characteristics of vacuum arc remelting process: Steel ingots after vacuum arc remelting have higher purity, lower gas content, less yttrium loss during smelting, and the chemical composition of finished steel ingots meets standard requirements.

[0145] The vacuum consumable electrode process includes the following steps: material preparation (φ360mm electrode rod) → cutting and peeling → welding auxiliary electrodes → vacuuming → leak rate detection → vacuum consumable smelting (until the electrode is completely melted) → cooling → demolding → turning → inspection → warehousing.

[0146] 1) Material preparation: Take out the finished φ360mm electrode rods from the warehouse and check their external dimensions and other parameters according to the technical requirements. They must meet the process technical requirements.

[0147] 2) Cutting and peeling: The outer circumference and end face of the φ360mm electrode rod are cut and ground by machine tool or by grinding machine. The grinding amount should be no less than 3mm, and the metallic luster of the electrode rod surface should be visible after cutting and grinding.

[0148] 3) Welding auxiliary electrode: Welding methods include manual arc welding, tungsten inert gas welding (TIG welding), and gas metal arc welding (MIG / MAG welding). The MIG welding material is φ1.2mm stainless steel welding wire. The welding current is 160-220A, the welding voltage is 20-25V, and the shielding gas composition is 80% Ar + 20% CO2.

[0149] 4) Vacuuming: Use a vacuum pump to evacuate the vacuum, and the vacuum level before arc initiation should be ≤1.33Pa.

[0150] 5) Leakage rate detection: Use a vacuum gauge for detection, and the actual measured leakage rate should be ≤0.133 Pa / min.

[0151] 6) Consumable metallurgy: A 5-ton vacuum consumable furnace is used for remelting. The melting rate is set to 2.7-3.7 kg / min and the voltage is set to 23V. The metal is melted by turning on the power.

[0152] 7) Cooling: First, cool with the furnace, preferably for ≥60 minutes, then remove the ingot and cool in the sheltered air.

[0153] 8) Demolding: This refers to removing the self-consumable smelted steel ingot from the ingot mold.

[0154] 9) Turning: The end face and outer circumferential surface of the φ423mm consumable ingot are machined by lathe according to the process requirements. The cutting amount is preferably 3-5mm.

[0155] 10) Inspection: Use a hand drill to collect chip samples from the consumable ingot and test their chemical composition;

[0156] 11) Warehousing: After passing the chemical composition and surface inspection, the finished steel ingots are put into storage, and the smelting qualification rate reaches 100%.

[0157] According to the aforementioned dual-vacuum production process, the smelting precision of yttrium can be effectively controlled, with the yttrium content controlled at 0.10%, and steel ingots that meet the standard requirements can be obtained.

[0158] The innovation of this invention lies in:

[0159] 1) During vacuum induction smelting, after pre-evacuating the vacuum to ≤10Pa, the induction furnace is powered on and the crucible is heated. The power should not exceed 250KW to melt the loaded material. After melting, the solution is stirred to ensure uniformity. At this time, the temperature of the melt is controlled at 1440-1530℃, and electromagnetic stirring is performed for at least 5 minutes.

[0160] 2) The melting temperature is controlled at 1490-1510℃, and the vacuum degree is not greater than 2.7Pa.

[0161] 3) After the finished sample meets the requirements, argon gas is introduced (high-purity argon gas is reintroduced into the vacuum chamber, and the operation should be carried out strictly in accordance with the specified argon gas pressure, steel liquid temperature and holding time). After argon gas is introduced, metallic yttrium is added. The amount added should be 0.50% to 0.60% of the calculated amount. The stirring time after adding metallic yttrium should be controlled to not exceed 5 minutes, especially 2-3 minutes.

[0162] 4) The electrode rod is cast in the induction furnace at a temperature of 1510±10℃.

[0163] 5) Consumable metallurgy: Vacuum consumable furnace is used for remelting. The melting rate is set to 2.7-3.7 kg / min and the voltage is set to 23V. The metal is melted by turning on the power.

[0164] In summary, the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for smelting a high-temperature resistant nickel-based alloy containing the rare earth element yttrium, characterized in that: This process includes vacuum induction smelting and vacuum arc remelting. First, it involves precisely controlling the target values ​​of elements such as C, Si, Mn, P, S, Cr, Ni, Cu, Al, Ti, Fe, Zr, and Y, with C being strictly controlled to the lower limit, specifically between 0.15% and 0.18%. Second, it employs strict control of the vacuum level during the smelting process to achieve precise control of the H, O, and N gaseous element content in the metal. Third, it strictly controls parameters such as stirring time and pouring temperature during vacuum smelting to precisely control the yttrium loss and meet the chemical composition technical requirements of 602CA.

2. The smelting method for the high-temperature resistant nickel-based alloy containing the rare earth element yttrium according to claim 1, characterized in that, The vacuum induction smelting process is as follows: material preparation → charging → pre-vacuuming → melting → vacuum preparation → melt cleaning → film formation, adding Al and Ti → taking pre-furnace samples → adjusting composition → taking finished product samples → purging with argon and adding metal yttrium → casting φ360-430mm electrodes → inspection and warehousing. Pre-vacuuming: After the furnace is closed after charging, a pre-vacuuming is performed with a vacuum degree ≤10Pa; The melting process involves: pre-vacuuming to ≤10Pa, then powering on the induction furnace and heating the crucible to a power not exceeding 250KW to melt the loaded material. After melting, the material is stirred at a melt temperature of 1440-1530℃ for at least 5 minutes using electromagnetic stirring. The vacuum preparation involves continuously drawing a vacuum, with a vacuum degree ≤ 2.7 Pa. The melting process is as follows: when the vacuum degree of the induction furnace reaches ≤2.7Pa, the power is increased to 1200KW; the melting temperature is controlled at 1490-1510℃, and the vacuum degree is not greater than 2.7Pa. The film formation process involves: when the induction furnace is powered off, gas is introduced to form a film on the surface of the high-temperature liquid after melting and clearing; then alloy materials such as Al and Ti are added according to the specified ratio. The adjusted composition: Based on the results of the pre-furnace chemical composition test, the composition is adjusted, and Zr alloy material is added according to the ratio; Argon purging and yttrium addition: after purging with argon, yttrium is added at a rate of 0.50% to 0.60% wt, and the stirring time after adding yttrium is no more than 5 minutes; The φ360-430 electrode is a solution-cast electrode rod in an induction furnace, with a casting temperature of 1440-1530℃.

3. The smelting method for the high-temperature resistant nickel-based alloy containing the rare earth element yttrium according to claim 2, characterized in that, The materials are prepared according to the requirements of smelting technology; the materials are pure iron, yttrium, chromium, titanium, zirconium, crystalline silicon, and nickel plate, and the content of each of the above elements is above 99%.

4. The smelting method for the high-temperature resistant nickel-based alloy containing the rare earth element yttrium according to claim 2, characterized in that, The loading process involves hoisting the prepared materials into the crucible in batches.

5. The smelting method for the high-temperature resistant nickel-based alloy containing the rare earth element yttrium according to claim 2, characterized in that, The pre-furnace sample collection involves taking a sample inside the furnace through a sampling window and performing chemical composition analysis.

6. The smelting method for the high-temperature resistant nickel-based alloy containing the rare earth element yttrium according to claim 2, characterized in that, The process of taking samples before furnace annealing involves purging with yttrium and adding metallic argon gas, followed by re-introduction of high-purity argon gas into the vacuum chamber. The argon gas strength is 15000-25000 Pa, the molten steel temperature is 1500-1520℃, and the holding time is 5-10 minutes.

7. The smelting method for the high-temperature resistant nickel-based alloy containing the rare earth element yttrium according to claim 2, characterized in that, The process involves purging with argon and adding yttrium, followed by stirring for 2-3 minutes.

8. The smelting method for the high-temperature resistant nickel-based alloy containing the rare earth element yttrium according to claim 1, characterized in that, The vacuum self-consumption process specifically includes: material preparation of φ360-430mm electrode rods → cutting and peeling → welding of auxiliary electrodes → vacuuming → detecting leakage rate → vacuum self-consumption smelting until the electrode is completely melted → cooling → demolding → turning → inspection → warehousing. Material preparation: finished electrode rods with a diameter of φ360-430mm, produced by vacuum induction casting; The welding auxiliary electrode has a welding current of 160-220A, a welding voltage of 20-25V, and a shielding gas ratio of 80% Ar + 20% CO2. The vacuum level before arc initiation is ≤1.33 Pa; The leak rate was measured using a vacuum gauge and was ≤0.133 Pa / min. The self-consumable smelting process involves remelting in a 5-ton vacuum self-consumable furnace with a melting rate set at 2.7-3.7 kg / min and a voltage set at 23V. The metal is melted by energizing the furnace. The cooling process involves: first, furnace cooling for ≥60 minutes, followed by air cooling after ingot removal.

9. The smelting method for the high-temperature resistant nickel-based alloy containing the rare earth element yttrium according to claim 8, characterized in that, The cutting and peeling process involves using a machine tool for overall cutting or a grinding machine to cut and grind the outer circumference and end face of the φ360-430mm electrode rod. The grinding amount should be no less than 3mm, and the metallic luster of the electrode rod surface should be visible after cutting and grinding.

10. The smelting method for the high-temperature resistant nickel-based alloy containing the rare earth element yttrium according to claim 8, characterized in that, The welding auxiliary electrode can be used for manual arc welding, tungsten inert gas (TIG) welding, and metal inert gas (MIG / MAG) welding. The MIG welding material is φ1.2mm stainless steel welding wire.

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